Low-temperature growth of GaAs polycrystalline films on glass substrates for space solar cell application

Preliminary results of growth of gallium arsenide poly-crystalline films on quartz glass substrate are reported. The films were grown using chemical beam epitaxy apparatus at substrate temperatures varied between 400 °C and 500 °C. The growth of polycrystalline GaAs has been realized at temperatures above 450 °C. X-ray diffraction (XRD) and Raman scattering show that the film grown at 500 °C has good crystallinity. Also, XRD and atomic force microscopy (AFM) have confirmed preferential columnar growth toward the 〈1 1 1〉 direction. Furthermore, AFM image reveals a naturally textured surface with a grain size of 0.5-1.0 μm. Optical energy gap, deduced from absorption coefficient of the film, is about 1.4 eV. Hall measurement indicates electrical properties such as resistivity, carrier concentration, and carrier mobility of approximately 10³ Ω cm, approximately 10¹⁵ cm^-3, and less than a few cm²/Vs, respectively. The results reveal future prospects of the film for application in space solar cells.