Investigations on Al$_{\bm x}$Ga$_{\bm {1-x}}$As Solar Cells Grown by MOVPE

Solar cells based on Al _x Ga _1-x As 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 _x Ga _1-x As solar cells with defect concentrations up to 1 × 10 ¹⁴ 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 _x Ga _1-x As solar cells with x ≥ 0.20. To overcome this issue, the n-doped Al _x Ga _1-x As As emitter can be replaced by an n-doped Ga _0.51 In _0.49 P heteroemitter. This heterojunction solar cell again shows overall defect concentrations below 1 × 10 ¹⁴ cm ^-3 and significantly improved cell characteristics.