Band Structure of Silicon, Germanium, and Related Semiconductors

A comprehensive survey of recent optical and cyclotron resonance experiments in semiconductors is given. By combining all available data, a categorical classification of eight principal levels in the valence and conduction bands of Si and Ge is proposed. Six of these levels occupy the same relative positions in the two crystals. Two of the levels are "sensitive" to the detailed differences in crystal potential; even these levels are much more nearly alike than previous theoretical work on Si indicated. The position of the two "sensitive" levels is shown to depend on one universal parameter, common to Si, Ge, and probably grey Sn, in both the experimental and theoretical band structures. The six insensitive levels are predicted quite accurately by theory.Experimental data on III-V compound semiconductors are consistent with the classification of levels in Si and Ge. It is suggested that a decisive test of the classification can be obtained from optical reflectivity studies of wurtzite crystals in the ultraviolet.