Mechanism of Carrier Transport in Hybrid GaN/AlN/Si Solar Cells

The particularities of the carrier transport in p–n-GaN/n-AlN/p–n-Si and n-GaN/n-AlN/p–n-Si structures were investigated through temperature-dependent current density and forward voltage (J–V) measurements, carrier distribution, and transport modeling. Despite the insulating properties of AlN, reasonably high current densities were achieved under forward bias. The experimental relationship between the current density and forward voltage was accurately approximated by an expression accounting for space-charge-limited current in the AlN layer and non-linear characteristics of the p–n junction formed in silicon. We suggest that extended defects throughout the AlN volume are responsible for the conduction, although the limited data available do not allow the accurate identification of the type of these defects.