Crystal growth of III-V materials on Si substrates for solar cell applications

Heteroepitaxial layers of GaAs have been grown on Si substrates by molecular beam epitaxy. In-situ thermal cycle annealing (TCA) and post-growth rapid thermal annealing (RTA) have been used to increase the crystalline quality of the heteroepitaxial layers. The transmission electron microscopy study revealed the annihilation of 60 degrees dislocations and the presence of stacking faults by TCA. RTA after TCA had resulted the layers free from stacking faults. The double crystal x-ray diffraction(DXRD) and photoluminescence (PL) have confirmed that prolonged annealing beyond 10 sec by RTA had no effect on the crystalline quality. The best full-width at half maximum values of DXRD and PL were obtained only for the TCA samples, as 127 are-sec and 2.6 meV respectively. The position of the band edge emissions, impurity and defects related emissions changes depending on the nature of annealing and has been attributed to the tensile strain variations in the epitaxial layers.