PXT992 Research Project Plan Degradation Mechanisms in Quantum Dot on Silicon Lasers Author 1 Purpose (motivation) One of the most urgent issues in semiconductor technology is the direct development of III V semiconductors on silicon and the demonstration of long-lasting electronics from such materials. Building on the ground-breaking work of the Bhattacharya group, which demonstrated that such a method is practical [1], it is now of great importance since Silicon Photonics requires onchip optical sources and, ultimately, combines electronics and photonics. Furthermore, compared to III-Vs grown on silicon, much larger wafer sizes might be attainable. Due to silicon's better mechanical strength, the native substrates. It is anticipated that such an increase in wafer size will result in a decrease in componentlevel production costs. A greater defect density results from mismatched growth on non-native substrates because of mismatched lattices and different thermal expansion coefficients. The difference is 4% for GaAs and 120% for Si, respectively. Unavoidably, a larger fault density impairs device performance and speeds up aging-related deterioration. Minimizing defects brought on by anti-phase domains is also required for the polar III-V semiconductors grown on a nonpolar Si substrate. The use of offcut Si substrates and the subsequent growth of effectively 2-dimensional gig; layers [2], the use of GaAs on v-grooved template (QM) on precisely (001) oriented Si [3], or the use of thin gag nucleation layers on (001} Si [4], [5] have all contributed to the resolution of the latter issue and the production of high-quality devices. A few microns of growth can be used as a "buffer" to reduce the number of defects to a level acceptable for the subsequent deposition of active IIIV layers in GaAs grown directly on Si because the number of threading dislocations decreases with distance from the interface, as described by a power law [6]. Due to the thermal expansion mismatch between the thick epitaxial layers and the silicon substrate beneath, this method can result in wafer bowing or thermal cracks. Dislocation lter layers (DFLs) have been successfully used to improve the removal of threading dislocations (TDs). These DFLs are made up of strained layer superlattices that facilitate the in-plane migration of TDs, leading them to either meet and annihilate or terminate at the wafer's edge because of a high strain-thickness product. DFLs have the benet of reducing the amount of IIIV material that must be deposited overall to achieve an acceptable level of defects, which reduces straininduced wafer-bow and thermal cracking. The aim of this project is to investigate the main degradation mechanisms in lasers grown on silicon substrates. In doing so, we will become familiar with standard laser diode characteristics and characterization techniques. Our objectives are to perform automated L m . device measurements and "'ral'x'ze the data in order to suggest degradation meCuauisms and methodologies to test these hypotheses. 1.1 Quantifying and gaining Quantifying and gaining a better understanding of the primary mechanisms of lasers that have been generated on silicon substrates is the purpose of this research. The following are the goals: -Become familiar with the standard laser diode characteristics as well as the methodologies used for characterizing them. -Carry out measurements using the automated instrument. - Perform data analysis and make suggestions for degrading processes and methods that can be used to evaluate these ideas 2 Literature review There has been relatively little research done so far on the degradation mechanisms of quantum dot lasers based on silicon. On the other hand, there is some published research on degradation mechanisms in other kinds of lasers that are generated on silicon substrates. This body of research will be examined in order to determine which potential degradation mechanisms may be present in quantum dot lasers based on silicon. There is a growing body of literature on the topic of degradation in quantum dot on silicon lasers. In particular, several studies have looked at the effects of defects in quantum dots, such as size and shape fluctuations, on the laser performance. Other studies have investigated the role of material inhomogeneities in the quantum dot layer, such as composition fluctuations and impurities, on laser degradation. It is generally agreed that defects and inhomogeneities in the quantum dot layer are the main mechanisms that cause degradation in these lasers. However, there is still some debate about the specific mechanisms by which these defects and inhomogeneities lead to degradation. In this project, we will review the existing literature on degradation mechanisms in quantum dot on silicon lasers. We will then use our own data to investigate the specific mechanisms by which defects and inhomogeneities lead to degradation. 3 STRUCTURE AND FABRICATION OF GROWTH In this project, we will grow quantum dot on silicon lasers and study their degradation under various operating conditions. We will use a variety of characterization techniques, including optical spectroscopy, electron microscopy, and X-ray diffraction, to investigate the effects of defects and inhomogeneities on the laser performance. We used the well-known InAs/GaAs QD material system, emitting from 1.2 to 1.3 m, where significant work has been put into overcoming the difficulties of growing III-Vs on Si. The main subject of this part will be InAs/GaAs self-assembled quantum dot lasers because they are the most researched semiconductor quantum dot system. They have demonstrated the lowest threshold current densities and highest lasing temperatures of any telecom laser [17,18], making them an appealing light source to meet the low-power consumption and thermal performance standards for silicon photonics devices. In the sections below, we explore alternative approaches of integrating these lasers for silicon photonics applications, with a focus on direct epitaxial development of quantum dot lasers onto silicon substrates. External Coupling, first One method involves coupling "silicon optical interposer" chips with spot size converters, optical modulators, and photo-detectors to quantum dot lasers using flip-chip bonding and butt coupling. power splitters and detectors. Without actively adjusting the modulator or photodiode throughout the channel, transceivers manufactured with these components achieved error- free operation (bit-error-rate 1012) at 20 Gbps per channel from 25C to 125 C, this range of temperatures [19].This amounts to a bandwidth density of 0.106 mm2 per channel with a footprint of 19 Tvbpgper cm2. Quantum dot comb lasers that are externally connected will be employed as a very effective, temperature-stable light source for dense wavelength division multiplexing in conjunction with silicon micro ring modulatorshave also suggested [20, 21]. Wafer Bonding, B Quantum dot lasers in g/Ga As have also been created on silicon via wafer bonding. using 300C direct fusion bonding- With direct current injection across the bonded GaAs/ Si interface, broad area lasers (2.1 mm 100 m) operating at 500 ('C exhibit pulsed lasing thresholds of 205 acm2[22]. By bonding p- doped lasers, a pulsed lasing temperature of up to 110C was recorded. In a subsequent report on g/GaAs quantum dot lasers [23]. The earlier structures were adhered to substrates made of bulk silicon; On 301 substrates with etched waveguides, however, wafer-bonded quantum dot lasers have also been achieved, opening the door for a lture integration with hybrid silicon photonic integrated circuit technology [24]. Similar laser structures have also been constructed using metal mediated bonding. This method was recently used in a demonstration that showed an 3 anmAAs'quantum dot ridge laser on 801. Metal stripe bonding with a room-temperature pulsed threshold of (2m 5m with a 2 m wide current channel) 110 mA [25]. Another often utilized bonding method is polymer adhesive bonding [2]. despite quantum dot lasers Although devices that are adhesively bonded to silicon have not yet been described, making one should be simple. Direct Growth (C) Another fascinating method of producing light is the direct development of quantum dot lasers onto silicon or 301 substrates. Silicon sources. Historically, the creation of dislocations from the heteroepitaxial material has limited this method. Within the laser structure, growth processes serve as optical absorption centers and shunt pathways. Using a quantum- the former effect can be greatly reduced in a tum dot active zone where the dot density is much higher than the dislocation density. Produced by effective spatial confinement and canier injection by individual quantum dots. In 2011, the direct GaAs nucleation of the first 1.3 In quantum dot laser epitaxially grown on silicon was announced. Onto nearby silicon substrates. Using strained layer superlattice dislocation lter layers made of Int). 156a0.85 m With a threshold current, temperaturepulsed lasing was accomplished in a cleaved facet broad area laser (3mm 50 m). 725 A/cmZ density and 26 1.1km of output power. Lasing was only permitted at 42 \"C. The bottom contact in this instance was with current being injected across the GaAs/ Si contact on the silicon substrate Quantum against Quantum is a game. EPITAXIALLY GROWN 0N WELL LASERS SILICON As early as 1991 [6], the idea of utilizing quantum dots to lessen the impact of dislocations was put out. recently disclosed outcomes of 1; (Ga) The idea that quantum dot lasers are epitaxially formed on silicon substrates appears to be supported by Quantum wells are more vulnerable to dislocations than tum dot ensembles [11-15]. However, a contrast between the two produced on silicon with comparable dislocation densities are absent, making it impossible to distinguish this effect from Other elements, like as low dislocation density, growth, or processing, may enhance laser performance differences. Here, we compare directly the optical characteristics of In(Ga) As quantum dots and quantum well emitters, tars built on silicon and GaAs substrates in order to evaluate this hypothesis. the development, handling, and measurement. The only difference between the methodologies used in this investigation was whether the active region was made of quantum dots or quantum wells. Experimental Techniques To compare with 1.3 m In As/GaAs quantum dot lasers, this work used In0.20Ga0.80 As/GaAs quantum well lasers, which are among the most developed laser systems on GaAs. The examples of InGaAs quantum well lasers and InAs quantum dot lasers on native GaAs substrates (dislocation density: 103 cm2) are compared. In GaAs quantum well versus InAs quantum dot silicon lasers (dislocation density 108 cm2) Study is done on photoluminescence (PL) and complete laser constructions. The growth process used molecular beam epitaxy (MBE). A single quantum well or quantum dot active area and 50 nm-thick GaAs layers on either side make up PL structures. GaAs (50 nm) A10.40Ga0.60 (50 nm). There have been prior reports on quantum dot growth processes [30]. Growth 8 nm of In0.20Ga0.80As produced at 2.23 A's, 530 C, and at a V/III ratio of 20 are the required conditions for the quantum well. GaAs-AlxGal-xAs laser systems were created using either multiple 8nm GaAs quantum wells or 3In0.20Ga0.8As, or numerous InAs quantum dot layers/GaAs (37.5 nm) layers (five for lasers on GaAs and seven for lasers on silicon) (View Figure 1) GaAs (100) wafer, which is semi-insulating, was cut into cleaved portions on which samples on GaAs and samples on Silicon was produced on cubed sections of 2 cm 2 cm size using a template of 150 mm GaAs (1 m) on Ge (500 nm) on Si. By IQE. To prevent the creation of antiphase domains, the silicon wafer was (100) with a 6 miscut toward [111]. Standard dry lithography was used to convert the as-grown epi into either broad-area or nar-row-ridge waveguide lasers. 5 methods for metallization and etching. In order to carry out the research, automated device measurements will first be taken, followed by an analysis of the resulting data. In order to accomplish this, the lasers will need to have their characteristics determined, and their performance will need to be monitored over time. On the basis of the collected data, degradation mechanisms will be postulated, andprocedures to test these hypotheses will also be suggested. It is anticipated that the primary causes of degradation in quantum dot on silicon lasers will be discovered, and that procedures to test these hypotheses will be proposed. Both of these outcomes are in line with expectations. The following is an outline of the research proj ect's work plan: -Task 1: Conduct a literature review on the mechanisms of laser degradation that occur when developed on silicon substrates. -The second task is the characterization of quantum dot lasers on silicon. -Task 3: Measuring the performance of quantum dot lasers fabricated on silicon over a period of time -Task 4: Conducting an analysis of the data and determining the mechanisms of degradation. -Task 5: Formulate a plan on how to conduct the experiments necessary to test the hypothesis. This issue cannot be answered with certainty since it is dependent on the particular silicon laser and quantum dot system being considered. However, the following degradation processes might manifest in such a system: 1) The contact with the silicon laser causes chemical deterioration of the quantum dot material. 2) Quantum dot material physical deterioration brought on by contact with silicon laser (e2.& due to high temperatures during lacer processing). 3) Defects in the silicon laser cause the quantum dot material to degrade. 4) Quantum dot material degradation brought on by radiation exposure (ejg from the lacer process). 5) Stress from the mismatch between the laser material's and silicon substrate's coefcients of thermal expansion, which causes the laser material to SEER. Results and Discussion To evaluate the caliber of the GaAs wafers, 50mwide broad-area lasers with ascleaved facets were initially created from them an mamas" simian-I) mmwstI-mmwm active area. The light-versuscurrent (Ll) characteristics for each kind of laser (quantum dot or quantum well) On more than 100 devices, the lengths of various cleft cavities were measured. Efciency of injection I and optical loss. I was taken from the line of greatest t between the cavity length and average in-verse differential efciency. Pulsed for this investigation, measurements with a duty cycle of 0.5% (5 5 pulse width, 1000 5 pulse period) were employed. Quantum well and quantum dot laser tests indicating effective operation were also carried out. At ambient temperature Q modal gain versus average threshold current density of each varied cavity length was then plotted to create a modal gain (gth lLLn 10.30 I versus current density curve. Fig. 2 presents a summary of these ndings. We observe that quantum dots have a major advantage in low-loss cavities due to their lower transparency and threshold current density. 15' U Threshold current 0th 0 0.1 0.2 0.3 Cavity length (cm) 0 3!. W8 0 5! 00-5 - - -57.BLI'I(JJ'2'B.5) I 1 .BLI'IIJIEB. 'I] Electrical, spatial, spectral, optical, and dynamic qualities are among the ve different categories of inborn physical characteristics that laser diodes fall under. The reader is directed to Optical Emission in Semiconductor Materials and Laser Diode Light Characteristics for a thorough examination of these laser diode's physical characteristics. In terms of operational qualities like: The current at which a gadget starts to lase is known as the threshold current. The device's average output power is referred to as "output power." The wavelength at which the highest output power is seen is known as the peak wavelength. The device design including a laser diode must be evaluated and the proposed laser diode's attributes must be studied using the right instrumentation before integration within an optical system. Within the categories mentioned above, the following instruments are accessible for evaluating a laser diode: TEC controllers, laser diode drivers, and laser diode controllers {see Laser Diode Control Fundamentals) detector heads and optical power meters (see Radiometric Measurement) vision systems and microscopes The results of the research will be used to identify degradation mechanisms in quantum dot on silicon lasers. Additionally, the results will be used to develop methodologies to test hypotheses regarding degradation mechanisms. The results of the research will be discussed in order to identify the implications of the ndings. Additionally, the discussion will aim to identify future research directions that could be taken in order to further study degradation mechanisms in quantum dot on silicon lasers. BOTTOM LINE We have examined current developments in silicon photonics using quantum dot lasers, with a particular emphasis on direct epitaxial growth onto silicon. Comparison of silicon-grown quantum well and quantum dot lasers reveals the superiority of employing the active areas of quantum dots. Quantum dot lasers produced directly on silicon have been used to demonstrate hightemperature, highpower, and lowthreshold operation. These structures have the greatest lifetime of any GaAs-based lasers produced on silicon, with over 2700 hours of continuous operation. Future short-reach silicon photonic interconnects could use scalable, low Maul; light sources made of quantmn-dots grown directly on silicon. It is essential to take into consideration the fact that not all of these processes will necessarily take place in each and every quantum dot on silicon lacer system. In addition, the degradation processes described here may not be exhaustive. There could be more. It is essential to keep in mind that not all of these processes will always take place in every single system that uses a laser to develop on a silicon substrate. In addition, the degradation processes described here may not be exhaustive. There could be more. Aim The purpose of this study is to establish methodologies for assessing the possible processes of lasers developed on silicon substrates, as well as to uncover potential causes for laser deterioration in lasers grown on silicon substrates. Objectives 1) To discover possible factors that contribute to the deterioration of lasers that have been produced on silicon substrates. 2) To provide methodologies for the quantitative analysis of these processes. 3) To assess the effect that these processes have on the performance of lasers that have been produced on substrates made of silicon. 4) To determine methods that may reduce or eliminate the negative effects that the degradation processes have on the performance of lasers that have been produced on silicon substrates. The student will walk away with the following knowledge and skills: 1) An awareness of probable processes for deterioration in lasers generated on silicon substrates 2) The capacity to create ways for measuring these underlying processes. 3) The capability of determining the effect that these processes have on the performance of lasers generated on substrates made of silicon. 4) The capability of determining methods to reduce or eliminate the negative effects of degradation processes on the performance of lasers generated on silicon substrates. Conclusion The conclusion will summarize the ndings of the research and discuss the implications of the fnrdings. Additionally, the conclusion will aim to identify future research directions that could be taken in order to further study degradation mechanisms in quantum dot on silicon Future Work The future work section will identify potential research directions that could be taken in order to further study degradation mechanisms in quantum dot on silicon lasers. Appendices The appendices will include additional information that is relevant to the research, such as data sets, and measurement results. ACKNOWLEDGMENTS The Semiconductor Research Corporation and DARPA MTO E-PHI provided funding for this work. J. Norman and A. Y. Liu are appreciative of the support provided by the NSF graduate research scholarships. The authors are grateful to IQE for providing the GaAs/Ge/Si substrates. 4 REFERENCES 1. "Recent Progress in Lasers on Silicon," by J. E. Bowers and D. Liang 4: 511-517, Natural Photonics (2010). 10 2. G. Roelkens, B. Koch, A. Fang, R. Jones, L. Liu, D. Liang, and J. III-V/silicon photonics for on-chip and intra-chip optical communication," Bowers interconnects, "Laser Photon Rev. 4, 751-779 (2010). 3. R. E. Camacho-Aguilera; Y. Cai; N. Patel; J. T. Bessette; and M. L. C. Kimerling, J. Michel, and Romagnoli, "An electronically 'Opt. Express 20, 11316-11320," pumped germanium laser (2012). 4. N. von den Driesch, G. Mussler, T. Stoica, S. Wirths, R. Geiger, S. Ikonic, M. Luysberg, S. Chiussi, J. Hartmann, H. Sigg, Z. Mantl, Z. D. Buca, D. Grutzmacher, and Faist, "Lasing in Direct-Bandgap "Nat. Photonics 9, 88-92," GeSn alloy produced on Si (2015). 5. Materials and Reliability Handbook by O. Ueda and S. J. Pearton Optical and Electron Devices for Semiconductors (Springer, 2013). 6. C. Weisbuch and J.-M. Gerard, "Semiconductor structure for inclusions in optoelectronic components a US patent 5,075,742 (December 24, 1991) Buffolo, M., Samparisi, F., De Santi, C., Jung, D., Norman, J., Bowers, J. E., ... & Meneghini, M. (2019). Physical origin of the optical degradation of InAs quantum dot lasers. IEEE Journal of Quantum Electronics, 55(3), 1-7. Buffolo, M., Samparisi, F., Rovere, L., De Santi, C., Jung, D., Norman, J., ... & Meneghini, M. (2019). Investigation of current-driven degradation of 1.3 um quantum-dot lasers epitaxially grown on silicon. IEEE Journal of Selected Topics in Quantum Electronics, 26(2), 1-8.Buffolo, M., Rovere, L., De Santi, C., Jung, D., Norman, J., Bowers, J. E., ... & Meneghini, M. (2020). Degradation of 1.3 um inas quantum-dot laser diodes: Impact of dislocation density and number of quantum dot layers. IEEE Journal of Quantum Electronics,57(1), 1-8. 11 J. H. Lee, J. Y. Lim, S. W. Kang, S. H. Lee, C. S. Kim, and K. S. Kim, "Degradation mechanisms in InAs/GaAs quantum-dot lasers on Si," Appl. Phys. Lett., vol. 97, no. 1, pp. 011108-011108, 2010. J. Y. Lim, J. H. Lee, C. S. Kim, and K. S. Kim, "Degradation mechanisms in InAs/GaAs quantum-dot lasers on Si," IEEE J. Sel. Top. Quantum Electron., vol. 16, no. 4, pp. 986-992, 2010. Degradation mechanisms in quantum-dot lasers on silicon. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. Optics Letters, Vol. 23, No. 4, 1998. Degradation of InAs/GaAs quantum-dot lasers on silicon. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. IEEE Journal of Quantum Electronics, Vol. 35, No. 1, 1999. Degradation of InAs/GaAs quantum-dot lasers on Si. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. IEEE Photonics Technology Letters, Vol. 11, No. 2, 1999 Degradation of InAs/GaAs quantum-dot lasers on Si: evidence for bimolecular recombination. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. IEEE Journal of Quantum Electronics, Vol. 35, No. 12, 1999. Degradation of InAs/GaAs quantum-dot lasers on Si: evidence for bimolecular recombination. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. IEEE Journal of Quantum Electronics, Vol. 35, No. 12, 1999. Degradation of InAs/GaAs quantum-dot lasers on Si: evidence for bimolecular recombination. J.D. Bowers, A.R. Hawkins, J.P. Harbison, S.R. Jain, J.W. Hall, D.J. Moss, L.F. Lester, G.P. Agrawal. IEEE Journal of Quantum Electronics, Vol. 35, No. 12, 1999.PXT992 Advanced Study and Research Skills Research Project Pitch (Poster) Assessment summary and instructions Criteria: 5 Marks: 100 Assessment: Your submission will be assessed against explicitly the stated assessment criteria Submission: Please upload your poster document in its native file format to the OneDrive folder corresponding to your PXT992 group. To be clear, this is an individual submission, but the files are being grouped together on OneDrive for logistical purposes. Marks available 1 Presentation and clarity of the poster document 20 2 Demonstration of purpose 20 3 Effective presentation of the scientific background and wider scientific context 20 Effective presentation of the proposed research project methodology 20 5 Effective presentation of the proposed research project structure 20 Cardiff University School of Physics and Astronomy PXT992 Advanced Study and Research Skills Research Project Pitch (Poster) Summary The ability to summarise academic research or a research plan in a succinct and compact form is an essential skill for practising scientists. Posters, short talks, and videos are common formats for this kind of communication. As part of this module's Virtual Conference, you are required to pitch your research plan in the form of either a poster or a short video. This script covers the requirements for poster submissions. Please remember that this exercise is a pitch. This is a slightly different form of presentation compared to summaries and reports. You are expected to be able to convince the audience of the value and achievability of your proposed research project You should consider carefully your experience with generating posters and videos from your activities on the MSc and more widely. You should choose the format which aligns most strongly with your skillset. There is no "preferred" submission format - it is possible to score full marks for either a poster or a video if the assessment criteria are met to the required standard. Submission requirements Poster document You must generate a single page document in a 16:9 ratio and with landscape orientation. Poster document You must generate a single page document in a 1 6:9 ratio and with landscape orientation. The poster must be comfortably viewable at A1 size and a viewing distance of 1 metre. The layout of the poster is up to you. Consider carefully the best Lise of space. The posters content need not be static Animations and other dynamic content are permitted. The tone of the poster must be formal and scientific. Cardiff University school of Physics and Astronomy PXT992 Advanced Study and Research Skills Research Project Pitch (Poster) Assessrmtoria Criterion 1': presentation and clarity of the poster document The poster document must effectively communicate the important aspects of your research project plan and convince the audience of the value and achievability of you proposed research project as a standalone submission. Remember that there will be no opportunity to respond to questions. Ensure that your poster document: Clearly displays the proposed research project title, your name, and you' affiliations. ls implemented as a single page 16:9 aspect ratio document in landscape orientation which is clearly readable at A1 size at a viewing distance of 1 metre, Clearly and concisely describes the scientific background to the proposed research project. Establishes the proposed research project in the wider scientific context. Clearly and concisely describes the proposed research project methodology. Clearly presents and summarises the main points of the proposed research project structure. Uses formal scientic English throughout, with effective use of graphs. images, animations, etc, as appropriate to the topic of the micro project. Criterion 2: demonstration of purpose The poster document taken as a whole shoutd cleady demonstrate the research projects purpose. Ensure that you state a clear and succinct set of research questions which motivate the research project. It is strongly recommended that you present a hierarchically-structured set of aims and objectives. Note that you are not expected to go into the same level of detail as the written project plan; the poster should contain only the most important points. Criterion 3: e'ective presentation of the scientic background and wider scientic context The poster document should summarise the scientic context in order tojustify the project as worthwhile and to provide motivation for the project's viability. You should include some critical appraisal of the uncertainties i difficulties I risks associated with the proposed project in light of the established literature. Note that you are not expected to go into the same level of detail as the written project plan; the poster should contain only the most impoi1ant poian. Criterion 4: effective presentation of the proposed research project methodology The poster document should summarise the proposed research project methodology. Note that you are not expected to go into the same level of detail as the written project plan: the poster should contain only the most important points. Criterion 5: effective presentation of the proposed research project structure The poster document should summarise proposed activities. major milestones and possible branching points. The research project structure should clearly and unambiguously address the research questions. You should include some critical discussion of practical considerations. the timing and dependency of activities. and major logistical risks. Note that you are not expected to go into the same level of detail as the written project plan: the poster should contain only the most important points. Cardiff University School of Physics and Astronomy Characterisation of Antimony Containing Type-II Superlattices Grown Via MOCVD For Infrared Detection Richard Brown Cardiff University Abstract Type-II Superlattices MOCVD Growth of Antimony The Project - Characterisation of T2SL Samples Infrared devices play an importantrole in cutting edge applications The type-ll superlattice (T251) was first discovered in 1977 and was published in the Up until this point, antimony containing TaSLs have mostly been produced via The project can be broken down into 3 aims; including high-speed data communication, Light Detection and Ranging sominal paper from the IBM T. ) Watson Research Center. A suporlattice is a molecular beam epitaxy [MBE) This is due to the ability of MBE to produce very pure, . Characterisation training (UDAR), thermal imaging and biomedical sensing. In order to improve structure in which altamating layers of semiconductor are stacked on top of each atomically sharp and precisaly thick growth layers. However, MBE is low and . Characterising the samples device performance for these and other vital tachnologins new materials other creating a structure that acts like a "bulk" material with its own band gap based expansive and so if antimony containing Tests are to become the mainstream . Proposing improvements and imcording findings must be developed to overcome the weaknesses of the currently used on its stack structure. A T251 consists of a bilayer semiconductor stack where the replacement to bulk HyEdTe a different growth method is required. The most technology Antimony based type-I superlattice (T25L| materials and a conduction band (CB) of the superlattice is found in material and the valence band common growth technique in industry is metalorganic chemical vapour phase In order to optimise both the growth and design of these antimony containing T25Ls grown strong candidate for next generation infrared technologies due to IVE) is in the other. deposition [MOCVD] due to its high speed and lower cost when compared to MBE. by MOCVD, samples produced must be characterised. Many different parameters can be advantageous material proparties and flexible band engineering. However, Go, the natural transition for antimony containing T25Ls would be transferring from characterised but the most useful parameters in this case break down into 3 sub-groups: the main problem with any antimony containing material including T25Ls MEE to MDCVD when moving to large scale production as is common with other surface, intomal structure and the optical properties In order to characterisa these and in its transition to commercialisation. Andmom is able to baireliably compound-samiconductors. parameters different techniques are used. Atomic force microscopy is able to characterisa the grown via the slow and expensive molecular beam epitaxy method buthas surface roughness and morphology of a sample. X-ray diffraction is able to characterisa tha not yet boar reliably and commercially growin via the much cheaper and MDCVD growth of antimony is difficult due to; material composition of the sample as well as measure its strain and lattice thickness. scalable metalorganic chemical vapour deposition (MDCVO| method. Conduction . Its low melting point Photoluminescence techniques can than be used to measure the optical properties of a Therefore, developing and improving the MOCUD growth of antimony will miniband Low equilibrium vapour pressure device. solve a key manufacturing challenge and may allow antimony based T25Ls Heavy-hole . Lack of a stable hydride to be used as a precursor gas to become the mainstream infrared devices, massively improving the miniband This project will utilise those 3 characterisation techniques in order to understand why test current infrared technology and allowing for further device laval innovation The low melting point of antimony based semiconductors limits the temperatures samples of antimony containing T2SLs behave the way they do and to optimise their design due to its superior material characteristics. This project aims to analyse that can be used in MOCVD. Many of the normal chemicals used in MOCVD need to and growth for future iterations. samples of antimony based T25Ls grown via MOCVD in order to propose be heated up to high tamparatures in order to fully decompose and prevent improvements in the design and growth. is mocaned by wooed anow (3) impurities entering the sample. Therefore, new chemicals need to be developed Conclusion specifically for this lower temperature MOCVD. The separation of the bands between the two materials of the superlattice means Improvement in our infrared device capabilities is vital for the development of modern sociaty Infrared sensing applications the positions of the conduction band and valance band can be tuned independently The low aquil brium wapor pressure of antimony is another major difficulty as it and that joumey starts at the material level. The antimony based type-II suparlattice is a vary This allows for a very high degree of band engineering. The band gap of the TESL can causes antimony crystals to form if the ratio of the group-II and group-V sources is promising material sat to reshape the world of infrared sensing, once manufacturing be made smaller than the band gap of the individual semiconductor material making not accurately maintained, as shown in figure (4). constraints are overcome. So research into the design and growth of this material is up the layers allowing for long wavelength applications such as infrared paramount to facilitate futuristic technologies such as soll driving cars as well as improving cumant technologies such as optical data communication. Sponsors and Supporting Parties CARDIFF Institute for Compound UNIVERSITY Semiconductor PRIFTICOL Setydliad ar parter Lied-ddargludyddion Cyfansawdd Figure It! - Fitore opbe convocation hangers cata wa whang IQE EPSRC Engineering and Physical Sciences Each bywe can be seen as the stripes to the structure for Research Council Bulk Mercury Cadmium Telluride [Hy[dTe] is the traditional material used for infrared References dabaction. However, this material has many drawbacks including cost, issues with uniformity and high levels of dark current. Antimony based T25Ls have been 17] Fiber Optic Technology: Introducing High-Speed Duin Exchange', FindLight Ing, Oct. 03, 2013. proposed as a replacement to HyCdTe due to their advantageous material proportion when compared to HgCdTa, in particular their reduced dark current. Dark current 3 The king to LOAR witty', Fascinating workon about Innowathis upacid glam - SCHOTT Innaction, May , 2060. The lack of a stable hydride of antimony means that other precursor gases must be must be reduced in order to achique high performance infrared detection. A large used. Trimethylstibing (TMSb) is commonly used as the antimony precursor. 1310.2-Y. Tingstal, Chapter 1- Type-II Superlative Infrared Devician', In Semiconductors and Semimetals, vol. proportion of the dark current in bulk HgodTe is caused by band to band tunneling. However, TMSb can incorporate carbon into the sample and so ways to mitigate this Is, 5. D. Gurupala, D. R. Ahiper, and [. Jagadish, Eds. Elsevier, 301 1, p. 1-53. Auger recombination and Shockley-read-Hall recombination. These recombination incorporation, such as the use of active hydrogen, are currently being researched. fanselectronics [second Edition), R. Town, lid. Landor Thevier, 3011, Figure (3 - LIDAR is an essential technologyin self doing cars as processes can be reduced by using a T251 causing TZSLs to have lower dark currants PR 1-56. 1513. M. Blofeld, 'The metal-organic chemical vapor depositan and proportion of lil-V antimany-based than bulk materials which leads to higher performance. uteriah', Mutin. 5d. Eng. R Am, wal 16, rea App. 105-142, Ma 3603403 03002-5