A major challenge in GaN based solar cell design is the lack of holes compared with electrons in the multiple quantum wells (MQWs). We find that GaN based MQW photovoltaic devices with five different Mg-doping concentrations of 0 cm^-3, 5×10¹⁷ cm^-3, 2×10¹⁸ cm^-3, 4×10¹⁸ cm^-3and 7×10¹⁸ cm^-3in GaN barriers can lead to different hole concentrations in quantum wells (QWs). However, when the Mg-doping concentration is over 1×10¹⁸ cm^-3, the crystal quality degrades, which results in the reduction of the external quantum efficiency (EQE), short circuit current density and open circuit voltage. As a result, the sample with a slight Mg-doping concentration of 5×10¹⁷ cm^-3exhibits the highest conversion efficiency.

The GaN based blue light emitting diodes (LEDs) with a thin AlInN layer inserted in front of the electron blocking layer (EBL) are experimentally studied. It is found that inserting a thin EBL can improve the light output power and reduce the efficiency droop compared with the conventional AlGaN counterparts. Based on numerical simulation and analysis, the improvement on the electrical and optical characteristics is mainly attributed to the reduction of the electron leakage current, which increases the concentration of carriers in the quantum well (QW) when the thin AlInN layer is used.