Degradation of II-VI ZnSe-Based Single Quantum Well Light-Emitting Devices

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Abstract
Degradation of ZnSe-based light-emitting devices (light-emitting diodes and diode lasers) are reviewed. These devices quickly degrade (i.e., show a decrease in the amount of light emitted) during continuous operation at room temperature. The best lifetimes are currently only a few hours for cw diode laser operation. Degradation of ZnSe quantum-well devices are shown to correlate with the current density necessary for operation and with the density of preexisting defects. The temperature of the quantum well during operation has been shown to be >250°C. The decrease in light emission correlates with the development of dark spot defects (DSDs) and dark line defects (DLDs) in or near the active quantum-well region of the device. It is shown that stress in the quantum well is not relaxed until late in the degradation process, and then only partially. Instead, the mechanism of degradation is shown to be the injection of point defects due to nonradiative relaxation processes, which ultimately collapse into the DSDs and DLDs. Methods to reduce the degradation of these devices are discussed.