Selenium Doping in GaAs Grown by Molecular Beam Epitaxy

Abstract

Using elementary Se as n-type dopant, Se-doped GaAs films were grown by molecular beam epitaxy. Characteristics of the films can be classified according to the amount of Se doped into areas where carrier concentration increases linearly [area I] (Se concentration ≤4 ×10 18 cm -3 ), saturates [area II] ( 4 ×10 18 –1 ×10 20 cm -3 ) and decreases [area III] ( ≥1 ×10 20 cm -3 ). In each area, we found a close correlation between electrical activity and photoluminescence spectra. The activation ratio of Se donors was found to be high in the samples classified in area I. These samples showed an efficient photoluminescence, although the observed spectra included deep level emissions at 890 nm and 1050 nm in addition to the band-edge excitonic emission. For the samples in areas II and III, however, photoluminescence efficiency dropped considerably and only a broad band emission (1300–1500 nm) appeared. This broad band emission is probably caused by complexes that include Ga vacancies and Se atoms because distinct electron concentration saturation takes place in this region.