III-Nitride Double-Heterojunction Solar Cells with High In-Content InGaN Absorbing Layers: Comparison of Large-Area and Small-Area Devices

This paper investigates the molecular beam epitaxy (MBE) growth, material characterization, and performance testing of indium gallium nitride (InGaN)/GaN double-heterojunction solar cells. Structures with varying thicknesses and compositions of the InGaN absorbing layer are studied. The N-rich MBE growth at low temperatures enables the growth of thick 10% and 20% InGaN films with minimal strain relaxation and defect generation. The characteristics of both large-and small-area devices are compared. While leakage current and high ideality factors associated with the double-heterojunction structure remain issues as detected by I-V and concentration effect measurements, the double-heterojunction cell with a record-high In content of 22% shows a promising photovoltaic response.