Effects of Mg-doping concentration on the characteristics of InGaN based solar cells

A major challenge in Ga N based solar cell design is the lack of holes compared with electrons in the multiple quantum wells(MQWs). We find that Ga N 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-3 and 7×1018 cm-3 in Ga N 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-3 exhibits the highest conversion efficiency.