Impact of temperature-dependent hole injection on low-temperature electroluminescence collapse in ultraviolet light-emitting diodes

Optical and electronic properties of mid-ultraviolet light emitting diodes with a two-step p-AlGaN region are measured at temperatures from 8 to 300 K. While the electroluminescence intensity increases down to a temperature lower than that reported in InGaN light emitting diodes (LEDs), there is still a collapse at cryogenic temperatures. Capacitance-voltage measurements across the same range of temperatures reveal an increasing depletion region with decreasing temperature indicating that hole injection is a significant factor in the temperature dependent behavior, as well as the cause of electroluminescence collapse.