Temperature dependent current-voltage curves study of GaN-based blue light-emitting diode

We have investigated the current voltage curves of the GaN-based blue light-emitting diode (LED) at different temperatures. The LED chips were fixed in a closed-cycle He cryostat with temperature varying from 220 K to 300 K, and current voltage curves were measured with a source-meter. The current voltage curves can be divided into four parts: the tunneling current zone, the recombination current zone, the diffusion current zone and the series resistance zone. The transitions in voltage and current between the zones vary as the temperature increases. We fitted the ideality factor and saturation current of the GaN-based LED from the I-V curve data according to the SahNoyce-Shockley theory. The experimental results demonstrate that the ideality factor improves as the temperature reduces, as does the saturation current. The value of ideality factor is much bigger than 2.0 in our experiments. A PN-MQW combination heterojunction model is proposed to explain the high value of the ideality factor of the GaN-based LED.