Reuse of GaAs substrates for epitaxial lift-off by employing protection layers

We demonstrate repeated use of GaAs wafers for multiple growths by employing lattice-matched epitaxial protection layers to preserve the wafer surface in its original condition following their etch removal after growth. The protection layers provide a regrowth surface that eliminates the need for repolishing prior to subsequent growth. Between growths, the protection layers are removed by wet chemical etching. The resulting surface quality is examined using atomic force microscope and energy dispersive spectrometry. We show that the surface roughness, chemical composition, morphology, and electronic properties of the GaAs surface after protection-layer removal are comparable to that of the original substrate surface. We show that p-n junction GaAs solar cells grown on original and reused wafers have nearly identical performance with power conversion efficiencies of ∼23%, under simulated 1 sun illumination, AM1.5 G. The high power conversion efficiency of GaAs solar cells combined with reduced costs associated with multiple parent wafer reuses promise cost competitiveness with incumbent solar cell technologies.