Direct experimental observation of band‐structure effects in GaPxAs1−x : N alloys by radiative lifetime measurements

The decay time of the photoluminescence due to the recombination of excitons bound to nitrogen in GaPxAs1−x alloys (x≳0.55) at 4.2 °K has been studied by uv laser time‐resolved spectroscopy. Using hydrogen implantation in order to reduce greatly the nonradiative lifetime of the samples, we show that the measured decay time is the radiative lifetime τxR of the bound excitons. Its variation with alloy composition is in good qualitative agreement with theoretical predictions. The observed decrease of τxR when the alloy becomes richer in GaAs is due to the modification of the recombination transition rate when the Γ band gets closer to the X band (band‐structure effect).