NITROGEN ISOELECTRONIC TRAP IN GaAs.

Abstract

The authors report the pressure-induced formation of the N isoelectronic trap in GaAs and GaAs//1// minus //xP//x (x equals 0. 045, 0. 115). Nitrogen traps are well known in GaP and AlAs and certain of their alloys. But for x less than equivalent to 0. 22 in GaAs//1// minus //xP//x and for x less than equivalent to 0. 15 in Al//xGa//1// minus //xAs, N//x states of isolated N vanish from the energy gap in photoluminescence (PL). Consequently, the existence of N-doping and its possible role in the electronic structure of GaAs and GaAs-rich alloys had not been established. In this work we show from extensive PL and PLES that N impurities induce a 'deep-trap resonance' above the GaAs conduction band edge, which may be driven into the fundamental gap through applied hydrostatic pressure. Experiments were performed at 5K at up to 80 kbar in a diamond anvil cell. For low pressures shallow direct-gap excitons dominate PL, giving a linear GAMMA //1-gap variation of 10. 6 meV/kbar. The GAMMA //1// minus X//1 crossover occurres near 40 kbar: an X//1-gap dependence of minus 1. 4 meV/kbar is obtained.