Similar and dissimilar aspects of III-V semiconductors containing Bi versus N

We show through band structure calculations that III-V-Bi alloys, emerging as a new class of semiconductor materials, differ nontrivially from their counterparts III-V-N alloys which have been intensively studied in the past decade. For a prototype system, GaAs1-xBix with a small amount of Bi, a large band gap reduction, due to the shift of the perturbed host band edges, resembles the effect of N incorporation in GaAs, but GaAs1-xBix exhibits a number of striking differences from GaAs1-xNx: (1) Bi generates a resonant impurity state in the valence band as a strongly perturbed host state, while N produces a resonant impurity state additional to the host states in the conduction band; (2) Under pressure, the Bi impurity state sinks further into the valence band, while the N impurity state emerges as a bound state; (3) the spin-orbit splitting increases superlinearly with increasing Bi amount, while it decreases sublinearly with increasing N amount. Qualitative conclusions for III-V-Bi are generally applicable for other isoelectronic donors in semiconductors.