Isoelectronic impurity states in direct-gap III-V compounds: The case of InP: Bi

Abstract

The isoelectronic impurity Bi in the direct-gap III-V compound InP is studied by emission and absorption spectroscopy including magnetic-field, time-resolved, temperature- and excitation-dependent measurements. Doping with Bi gives rise to two emission lines, a sharp Bi "bound exciton" (Bi, $X$) and a broader $(\mathrm{Bi}, X)-(\mathrm{Bi}, X)$ bound-excitonic molecule. The hole of the bound Bi-exciton is extremely localized while the electron has a typical donorlike Bohr radius. Therefore the ${\mathrm{Bi}}^{+}$ behaves like a pseudodonor, in particular, in magnetoluminescence experiments. The $(\mathrm{Bi}, X)-(\mathrm{Bi}, X)$ bound-excitonic molecules resemble an ${\mathrm{H}}_2$-like "pseudodonor molecule." This new type of isoelectronic complex is investigated and discussed in detail.