High power UVB light emitting diodes with optimized n-AlGaN contact layers

The influence of the n-AlGaN contact layer thickness and doping profile on the efficiency, operating voltage and lifetime of 310 nm LEDs has been investigated. Increasing the n-contact layer thickness reduces the operation voltage of the LEDs and increases the emission power slightly. Optimizing the n-doping profile yielded enhanced conductivity and reduced operation voltage with a simultaneous output power enhancement of the LEDs. Lifetime measurements have shown that even though the output power of the LEDs was enhanced the lifetimes were not negatively affected. Room temperature photoluminescence indicates a low concentration of point defects in the n-doping region yielding minimum AlGaN resistivity.