ABSTRACT
The bandgap energy Eg(x) of a ternary compound varies with the composition x as follows: Eq. ( 1.1 ) ( ) ( ) 2g g 0E x E bx cx= + + where Eg(0) is the bandgap energy of the lower-bandgap binary compound and c is the bowing parameter. The bowing parameter c can be theoretically determined [Van Vechten and Bergstresser 1970]. It is especially helpful to estimate c when experimental data are unavailable. The lattice constant a of ternary compounds can be calculated using Vegard’s law. According to Vegard’s law the lattice constant of the ternary alloys can be expressed as follows: Eq. ( 1.2 ) ( )alloy A B1a xa x a= + − where aA and aB are the lattice constants of the binary alloys A and B. Vegard’s law is obeyed quite well in most of the III-V ternary alloys. The compositional dependence of the energy gaps of various III-V ternary alloys at 300 K is given in Table 1.2 [Casey and Panish 1978].
