QUESTIONS AND PROBLEMS 5.16 5.17 5.18 5.19 Doped GaAs Consider the GaAs crystal at 300 K. a. Calculate the intrinsic conductivity and resistivity. In a sample containing only 1015 cm³ ionized donors, where is the Fermi level? What is the conductivity of the sample? b. In a sample containing 1015 C. cm ionized donors and 9 x 104 cm³ ionized acceptors, what is the free hole concentration? Where is the Fermi level? Extrinsic III-V semiconductor GaAs is a III-V semiconductor. Suppose a GaAs crystal has been doped with Te atoms in the amount 1 x 1017 donors cm³ and Zn atoms in the amount 7 x 105 cm³. Is this an n or and p-type GaAs? The electron and hole drift mobilities in GaAs are given in Table 5.4. Find its resistivity. Compensation doping in GaAs Consider an n-type GaAs crystal that has been doped with 1 x 1016 donors cm³. Find the acceptor concentration you need to turn this n-type GaAs to p-type with the same resistivity as the n-GaAs. Use Table 5.4 for the electron and hole drift mobilities in GaAs. Varshni equation and the change in the bandgap with temperature The Varshni equation describes the change in the bandgap E of a semiconductor with temperature 7 in terms of AT2 E = Ego B+T atants For example, for