Photoinduced current generated by subband gap optical pumping for the investigation of deep levels in semiconductor lasers

It is shown that the measurement of photocurrents induced by optical pumping at subband gap wavelengths may be a useful technique for studying deep-level traps in semiconductor lasers. In this experiment a 1.3 μm wavelength laser is used to probe a 0.78 μm wavelength GaAs laser device. The trap density of a predegraded and postdegraded device was measured. The measurement indicates a significant increase in the trap density for the degraded device over the nondegraded device. Rate equations describing this excitation process are given and are shown to describe the experiment very well.