We report on AlGaAs‐based heterojunction solar cells grown by solid source molecular beam epitaxy (MBE). We investigate InGaP and AlGaAs material quality and we demonstrate significant efficiency improvements by combining the best of each alloy: a thick p‐AlGaAs base with tunable bandgap, and a thin 50 nm n‐InGaP emitter separated by a thin intrinsic AlGaAs layer. We report a certified solar cell conversion efficiency of 18.7% with a 2‐μm‐thick AlGaAs layer and a bandgap of 1.73 eV, suitable for high efficiency Si‐based tandem devices.

We study GaInP alloy grown by molecular beam epitaxy (MBE) for single junctions solar cells. Growth was optimized to obtain a photo-conversion efficiency of 9.66%, without anti-reflection coating. Further characterization allowed the investigation of the remaining issues in the structures. Beryllium doped GaInP base layer was identified as the layer limiting the photo-conversion performance of the solar cells.

Today's most efficient III-V solar cells rely on InGaP materials and are mostly grown by metal organic vapor phase epitaxy (MOVPE). Here, we report on an AlGaAs-based solar cell grown by solid source molecular beam epitaxy (MBE), with a certified conversion efficiency of 18.7%, and a 1.73eV bandgap designed for Si-based dual junction tandem devices. Material characterizations were carried out using Hall effect, secondary-ion mass spectrometry (SIMS) and X-Ray diffraction for the optimization of growth parameters of two conventional homojunction AlGaAs and InGaP solar cells. External quantum efficiencies (EQE) and I-V measurements demonstrate issues related to n-type AlGaAs and p-type InGaP layers. We show an important efficiency increase by merging the best of each structure: a thick p-AlGaAs base with tunable bandgap, and a thin 50 nm InGaP emitter.

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