Pressure dependence of theDXcenter inGa1−xAlxAs:Te

Abstract

The pressure dependence of the DX center in Te-doped ternary alloy ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Al}}_{\mathrm{x}}$As with x=0.15, 0.25, and 0.35 has been studied. The pressure coefficients of the activation energies for emission and capture as well as the pressure coefficient of the thermal ionization energy were found to change sign when the band gap of ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Al}}_{\mathrm{x}}$As changed from direct to indirect. The compositional dependence of these energies at atmospheric pressure has also been extrapolated from the pressure dependence. Similarities between the effects of changing pressure and Al mole fraction suggested that the properties of the DX center depend mainly on the host semiconductor conduction-band structure. The difference in the pressure dependence of the DX center when the band gap is direct as opposed to indirect suggests that the defect wave function has considerable contribution from the conduction-band minima near the X point of the Brillouin zone and not just from the L-point minima as has been proposed by many authors.