Auger recombination in GaAs and GaSb

In highly excited GaAs and GaSb luminescence bands above the band gap at $h\nu =E_g+{\Delta }_0$ are observed, which are explained by radiative recombination of Auger-excited holes in the split-off valence band with free or shallow bound conduction-band electrons. An extremely weak luminescence continuum in both materials between $h\nu =E_g$ and $h\nu =2\mathrm{}{E}_g$, which shows no distinct structure within the experimental resolution, is ascribed to the radiative recombination of relaxing Auger electrons in the conduction band. The role of the split-off valence band for hole-hole-electron (hhe) Auger recombination is explained. From spectroscopic data the hhe Auger coefficients $C_p$ for GaAs [$C_p{\left(\mathrm{GaAs}\right)}_{77 \mathrm{K}}\approx {10}^{-(31\mathrm{}\pm 1)}$ ${\mathrm{cm}}^6$ ${\sec }^{-1\mathrm{}}$] and for GaSb [$C_p{\left(\mathrm{GaSb}\right)}_{77 \mathrm{K}}\approx {10}^{-(25\mathrm{}\pm 1)}$ ${\mathrm{cm}}^6$ ${\sec }^{-1\mathrm{}}$] are estimated, in rough agreement with theoretically predicted values. The dependence of the luminescence intensities of the investigated emission bands in GaSb at $E_g$ and at $E_g+{\Delta }_0$ on the exciting light density and on the doping concentration leads to the conclusion that in $p$-type GaSb band-to-band Auger recombination occurs. The surprisingly high intensity of the emission, which is connected with a hhe Auger process, in $n$-type GaSb(Te) and its strange dependence on the excitation power is explained by a band-to-acceptor Auger process. It is believed that this acceptor is the doubly ionizable native defect in GaSb, which is always present.