Asymmetrical quantum well degradation of InGaN/GaN blue laser diodes characterized by photoluminescence
The temperature, power, and voltage dependent photoluminescence spectra are studied in InGaN/GaN double quantum well blue laser diodes. Emissions from the two quantum wells can be distinguished at low temperature at low excitation power density due to the different built-in electric field in the two quantum wells. This finding is utilized to study the degradation of InGaN/GaN blue laser diodes. Two peaks are observed for the non-aged laser diode (LD), while one peak for the aged LD which performed 3200 h until no laser output is detected. The disappearance of the high energy peak in the photoluminescence spectra indicates a heavier degradation of the quantum well on the p-side, which agrees with our previous observation that both the linewidth and the potential fluctuation of InGaN quantum wells (QWs) reduced for the aged LDs.