Temperature dependent electroluminescence measurement of AlGaN-based ultraviolet light-emitting diodes

Advances in AlGaN-based mid-ultraviolet (<; 290 nm) light emitting diodes (LEDs) have produced compact light sources with efficiencies approaching 4% [1,2] Efficiencies still greatly lag behind those of InGaN-based visible LEDs however, for a number of reasons. Among these is the reduced doping efficiency and carrier mobility of high-Al content AlGaN, especially in the p-type, magnesium doped layer above the active region. Polarization doping has been proposed [3] as one method for increasing the electrical conductivity in this layer. Commercial devices currently include a series of layers stepping down in composition from the electron-blocking layer to a p-GaN contact layer, and as such may already benefit from a small polarization doping effect. Were this the case, low-temperature electroluminescence should show an increase in output power, as the hole mobility and concentration would not freeze out at cryogenic temperatures.