Unique temperature dependence of deep ultraviolet emission intensity for diamond light emitting diodes

Abstract

We have observed the temperature T (25–200 °C) dependence of the electrical and optical properties of diamond deep-ultraviolet (DUV) light emitting diodes (LEDs). The current–voltage characteristics showed a rectification ratio of 108 at ±20 V throughout the T range. In this LED, a strong DUV (235 nm) emission intensity due to free exciton radiative recombination was observed. At a constant injection current of 300 mA, the DUV emission intensity became four times larger at 200 °C than at 20 °C, that is, the external quantum efficiency of the diamond DUV-LED increases as T increases. This result is the converse of the T dependence trend of commercially available LEDs. A study of the T dependence of light extraction efficiency showed that this unique behavior is mainly due to the T dependence of the internal quantum efficiency of the diamond LED.