Electronic transitions in bulkAl0.3Ga0.7As under hydrostatic pressure

We present a study of the radiative transitions in ${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As under hydrostatic pressure in the range 0–70 kbar using photoluminescence at 15 to 125 K. A new trapping center is reported. The center forms an efficient carrier trap, and produces a pressure-induced hysteresis in the intensity of the radiative transitions. A generic large-lattice-relaxation model with an unusually large emission barrier is proposed to understand the strong hysteresis. We postulate that the center is higher than the X conduction band at ambient pressures, and present arguments to show that it is indeed a different center, not caused by either the DX or the shallow-donor centers. We have also obtained pressure coefficients of several direct and indirect transitions. The activation energies of various radiative transitions and an understanding of the scattering processes at chosen pressures is obtained from the temperature dependence of the luminescence intensities.