Heterojunction Diode You are given an P-n heterojunction shown below. The materials parameters you need for this problem are as follows. GaN:Eg=3.4eV,me=0.2, mhh=1.5,mlh=0.3,r=9.5, spontaineous polarization =2106C/cm2.Al0.3Ga0.7N:4.24eV,EC=0.67eV, me=0.26,mhh=2.11,mlh=1.27,r=9.4, spontaineous polarization =2.04106Ccm2 (This isn't correct, but it makes things easier!). AlGaN and GaN exhibit spontaneous polarization and piezoelectricity. Let's consider only polarization for the moment. Changes in polarization result in charge, given by: =P Where is the volume charge, and P is spontaineous polarization. 1. Find the built-in voltage, and at zero bias plot the charge diagram, appropriate electric field diagrams, band diagram, and find the depletion width. 2. Now the heterostructure composition is linearly graded from Al0.3Ga0.7N to GaN over a region 20nm thick. Assume that the materials parameters are linear with composition. Find the built-in voltage, and at zero bias plot the charge diagram, appropriate electric field diagrams, band diagram, and find the depletion width