Keywords: rough silicon, molecular beam epitaxy, GaAs, solar cells, structural properties, electronic properties, gallium arsenide, defect density, minority carriers, nanotechnology
Relationship between the structural and electronic properties of n–GaAs layer grown on rough Si substrate by molecular beam epitaxy
The relationship between the electronic and structural quality of n–GaAs layer grown by Molecular Beam Epitaxy (MBE) on rough silicon surface substrate (RSi) was investigated by Reflection High–Energy Electron Diffraction (RHEED), Time–Resolved Photoluminescence (TRPL), High–Resolution X–Ray Diffractometer (HRXRD) and photocurrent spectroscopy. The results demonstrate a high correlation between the defect density and the minority carrier lifetime, showing that the defect density is a strong cause for trapping the minority carriers. Atomic Force Microscopy (AFM) and HRXRD analysis show a flattening of GaAs film on rough Si substrate. The minority carrier lifetime is enhanced when the GaAs layer is grown on RSi. This enhancement was explained by the minimisation of the defect density when using the rough surface. The improvement of minority carrier lifetime is at the origin of enhancement of photo–carrier collection.