physics and applications of semiconductor microstructures 연습문제 풀이(1~5장)
5.4 Use table 5.1 to relate the dielectric constant and the observed and calculated forbidden gaps in materials consisting of atoms from the same row of the Periodic Table. List these materials in the order of increasing ionicity. Explain the result in simple qualitative terms.
GaAs is more ionic than Ge and ZnSe is more ionic than GaAs
5.5 The density of electron states was defined as the number of states in a unit energy interval. Inspect visually the band structures in Fig. 5.3 to identify the transition energies (gaps) at which a large density of states should occur. How does this affect optical properties of these material?
The conduction band minima near the X and Γ points. The optical transitions across the 9vertical) gap at these points will be strong
5.6 Find a compound semiconductor or a semiconductor alloy such that the material is likely to be an efficient absorber of visible light in the res region of the spectrum.
The fundamental gap is hc/λ; λ≅6200Å gives an energy of about 2eV.
We need, for instance, a Zn(0.5)Cd(0.5)Te alloy. Neither Si nor GaAs would do.
5.7 Find the concentration of phosphorus in GaP(x)As(1-x) such that the lowest states of the X and Γ valleys occur roughly at the same energy. What is the lattice constant of this alloy?
physics and applications of semiconductor microstructures