(a) Explain what is meant by a type I and type II and type III semiconductor hetero junction. (b) Consider the flat band heterojunctions, System A and System B, shown

inFigure Q3.1. Calculate the conduction and valence band discontinuities for each. (c) A semiconductor light emitting diode is required to emit light with a wavelength of2.5 µm. However, InP must be used as the substrate. Using Figure Q3.2 below,suggest all suitable semiconductor compounds that could be used, estimating theirapproximate composition. Comment on the suitability and the costs of eachrealistic solution in no more than 200 words. Figure Q3.2: Minimum energy band gap and wavelength of a light from the semiconductor bandgap as a function of the lattice constant. The full lines are for direct semiconductors and the dash lines for indirect semiconductors. (d) Using the WKB approximation, show that the transmission probability ( 7) of an electron of energy (E) incident on the potential barrier shown below is given by: T=\exp \left\{-\frac{2 w}{3 V_{0}}\left(5 V_{0}-2 E\right) \sqrt{\frac{2 m}{\hbar^{2}}\left(V_{0}-E\right)}\right\} Write in no more than 50 words comments to your solution and why you think this is the best way to obtain the answer.