Numerical Study of the Effects of Hetero-Interfaces, Polarization Charges, and Step-Graded Interlayers on the Photovoltaic Properties of (0001) Face GaN/InGaN p-i-n Solar Cell

The photovoltaic properties of (0001) face GaN/InGaN p-i-n solar cell are studied numerically. The simulation results show that the detrimental effects of hetero-interfaces and polarization charges will seriously degrade the solar cell performance, especially when the indium composition is high. If these effects are not eliminated or diminished, the photovoltaic properties would not be good enough for practical applications even if a high-quality crystal could be obtained. For this purpose, the step-graded interlayers between the GaN-InGaN interfaces are introduced in order to overcome both aforementioned critical effects. The impacts of the thickness and p-type doping concentration of the step-graded interlayers are also investigated in detail.