Investigations on Al Ga As Solar Cells Grown by MOVPE

Solar cells based on Al_xGa_1-xAs in its direct bandgap range were fabricated and analyzed. We show that state-of-the-art metalorganic vapor phase epitaxy systems and precursors are capable of growing Al_xGa_1-xAs solar cells with defect concentrations up to 1 × 10¹⁴ cm^-3 and less determined by deep level transient spectroscopy. However, for the n-doped material, inevitable DX-centers exist. These dopant-related defects limit the performance of the investigated Al_xGa_1-xAs solar cells with x ≥ 0.20. To overcome this issue, the n-doped Al_xGa_1-xAs As emitter can be replaced by an n-doped Ga_0.51In_0.49P heteroemitter. This heterojunction solar cell again shows overall defect concentrations below 1 × 10¹⁴ cm^-3 and significantly improved cell characteristics.