The effect of mounting-induced strain and defect on the properties of AlGaAs 808 nm LDs

The effects of the mounting process on the properties of broad-area AlGaAs SQW 808 nm high-power laser bar were investigated using electroluminescence microscopy (ELM), micro-photoluminescence (μ-PL), photoluminescence microscopy (PLM) and micro-photocurrent (μ-PC) spectroscopy. Local strain and V-shaped defects were observed as a function of position by μ-PL and PLM, respectively. ELM images from each emitter were taken as a function of bar injection current, allowing the determination of the “apparent” external differential quantum efficiencies (ηext). The results suggest that there is a strain threshold, above which ηext decreases with increased strain. μ-PC measurements show that the emitters with defects have a larger PC tail in the sub-bandgap region. The peak position of the first derivative (dIPC/dE)max of the PC spectra displays a blue shift with the increase of strain. The magnitude of the (dIPC/dE)max has a weak inverse correlation with strain. The results suggest that with the increase of strain up to threshold, defect-related non-radiative recombination centers form and accumulate. The increased non-radiative recombination results in the decrease of ηext of the emitter, i.e., the degradation of the emitters and the bar.