InGaN/GaN Multiple Quantum Wells solar cells: a trade-off in p-GaN thickness, to optimize reliability and quantum efficiency

By extensively characterizing, modelling and investigating the degradation of high periodicity InGaN/GaN Multiple Quantum Wells (MQWs) GaN-based solar cells, we revealed a trade-off for defining the thickness of the p-GaN layer. By submitting these devices to constant optical power stress at high excitation intensity and high temperature, and through by an appropriate fitting of the degradation kinetics according to Opdorp and t’Hooft and Orita models, we identify the presence of a thermally activated diffusion process, which is responsible for device degradation. We also found that a thicker p-GaN layer reduces the amount of impurities which diffuse to the active region (AR) of the device, resulting in a lower degradation, thus increasing reliability and stability under harsh environment applications. In contrast, according to a detailed quantum efficiency model, we found that a thinner p-GaN layer allows to increase the efficiency in the UV spectral range, resulting in a p-GaN thickness trade-off between reliability and quantum efficiency.