Non radiative recombination at DX centre in Al sub x Ga sub 1-x As grown by molecular beam epitaxy

The emission and capture properties of Si-DX centre in Al sub x Ga sub 1-x As grown by MBE have been studied over the composition range (0<x<0.84). Only a single DX centre peak has been detected. The thermal activation energy is found to be 0.42+- 0.02 eV, independent of alloy composition over the range 0.3<+< 0.854. Capture cross section measurements reveal that the electron capture cross section of the DX centre is thermally activated, the thermal capture activation energy, E sub a being 220 +-30 MeV. The hole capture cross section of the DX centre is reported here for the first time and is measured to be σ sub p = 2.4x10 sup -14 cm sup 2, independent of temperature. Recombination calculations show that the DX centre is likely to act as a strong nonradiative recombination centre at room temperature. The hole capture cross section measurements support the negative U model for the DX centre. (author)