Influences of the p-GaN Growth Temperature on the Optoelectronic Performances of GaN-Based Blue Light-Emitting Diodes

Abstract

We investigate the influence of p-(Al)GaN growth temperature ( $T_{g}$ ) on the optoelectronic performances of InGaN/GaN multiple-quantum-well (MQW) blue light-emitting diodes (LEDs). We systematically combine various characterization techniques, such as current–voltage, current-light output power, capacitance–voltage ( $C$ – $V$ ) under forward and reverse biases, photocurrent and electroreflectance (ER) spectroscopies, temperature-dependent electroluminescence, and the internal quantum efficiency (IQE). From the experimental analyses, it is shown that increasing $T_{g}$ induces: 1) the reduced optical loss by the improved crystal quality of the p-GaN layer (improved light extraction efficiency) and 2) the decreased IQE due to the Mg diffusion from the p-(Al)GaN layer to the MQW region. This paper demonstrates that the fine control of the Mg diffusion from the p-GaN layer to the InGaN/GaN MQW region is the key factor for achieving highly efficient blue LEDs. Moreover, a method of estimating the Mg diffusion length is proposed for the first time by analyzing both the $C$ – $V$ curves and the ER spectra under reverse biases.