Influence of crystal orientation of the growth surface due to molecular beam epitaxy on the optical properties of Si-doped GaAs layers

Photoluminescence (PL) spectra of GaAs (100), (111)A and (111)B layers grow n by molecular-beam epitaxy at different ratios of the partial pressures P- As4/P-Ga = gamma are investigated. Depending on the crystal orientation and gamma values, either two PL bands (B- Si bands) or a single PL B-band are observed. The B-band corresponds to band-to-band radiative recombination (e --> h) and the Si band is attributed to optical transitions between the co nduction band and the Si acceptor states (e --> A). The observed variations of the PL spectra and of the type and magnitude of the electrical conducti vity as functions of the orientation and gamma value are interpreted in ter ms of changes in the Si-acceptor concentration and their energy spectrum as well as a change in the ratio of the concentrations of the Si donor and ac ceptor states. These results are explained in the framework of the kinetic approach based on the multiplicity (energy) of the dangling chemical bonds on the different surfaces, with the influence of the molecular flux densiti es taken into account. (C) 1998 American Institute of Physics. [S1063-7826( 98)00711-X].