Deep level transient measurements of DX centers in GaAlAs up to room temperature

DX centers were investigated in Si doped Ga0.4Al0.6As by capacitance-voltage (C-V) characterization, by deep level transient spectroscopy (DLTS), and by fast defect transient (FDT) measurements. Since the last method is capable of measuring transients in micro- and nanosecond ranges, it allowed us to measure transients of DX centers up to room temperature. The investigated samples were laser structures where only the cladding layer is doped by Si, so the DX centers are localized within a few Debye lengths in the vicinity of the depleted layer edge. The capture and emission activation energies determined by capacitance DLTS and by FDT measurements are in agreement with the values reported in the literature, in contrast to our previous FDT measurements in bulk GaAlAs samples. The results suggest that the DLTS signal is dominated by transients in the vicinity of the depleted layer edge even in bulk samples. The differences between FDT measurements in bulk and laser structure samples are explained by the recently proposed Auger capture model of the DX shallow–deep transition.