Solid state physics

Semiconductor heterostructures The GaAs and AlGaAs semiconductors are given below. For the following parts of the task, these may be doped as desired. For the following parts of the task, draw everything that would be found in a hetero band structure. a) What would be the best combination of these semiconductors to operate an infrared LED? b) In the lecture, it was shown in an experiment that an LED changes colour when it is immersed in liquid nitrogen. What is the reason for this? What is the physical background to this? c)How would the semiconductors below have to be combined to obtain a two-dimensional electron gas? Draw this schematically 'il vauuum level 1 conduction band 2 \\ valence band \\1 Golf's NW3