Diffusion in the III–V Compound Semiconductors

Abstract

Of the various compound semiconductors, the III–V compounds have properties most similar to the group IV elemental semiconductors. Like Si and Ge, the III–V compounds may readily be doped as n- orp-type to form p-n junctions, the most useful and widespread application of semiconductors. They are 1-to-l chemical compounds of the group III elements B, Al, Ga, and In with the group V elements N, P, As, and Sb. The III–V compounds are tetrahedrally coordinated, and the majority crystallize in the zinc-blende structure illustrated in figure 6.1 for GaAs. The zinc-blende structure is the diamond lattice of Si or Ge, but with group III and V atoms occupying adjacent lattice sites. Although the diamond and zinc-blende structures are similar, the differences in lattice constant, the presence or absence of d-shell electrons, and the ionicity of the III–V compounds result in significant differences in the band structure [1]. The varied band structures and large range of energy gaps possible with the III–V compounds have led to many potential applications. The crystal structure, lattice constant, type of energy gap, and the room temperature energy gap are summarized in Table 6.1 for the elemental semiconductors Si and Ge and the III–V compound semiconductors.