Novel features of photoluminescence spectra from acceptor-doped GaAs: formation of acceptor—acceptor pair emissions and optical compensation effect

Low temperature photoluminescence measurements were carried out for acceptor-doped GaAs. Impurities were introduced by doping during molecular beam epitaxy (MBE) or liquid phase epitaxy (LPE) growth or by ion beam impingement into substrates using mass-separated ions. In the case of carbon incorporation, doping of mass-separated C+ ions using a low energy ion beam was carried out during MBE growth of GaAs. Results revealed that just below the band edge emissions a large number of novel strong emissions are produced. These emissions were found to be totally missing in specimens prepared by conventional methods. Dual incorporation of acceptor and donor impurities indicated that these emissions are easily quenched by an extremely small amount of donor atoms, which is a principal reason for the absence of these emissions in previous samples. Most of these novel emissions were also obtained in InP, implying that these observations are ubiquitously established in the whole range of III–V compound semiconductors. It was concluded that for the comprehensive understanding of impurity properties in semiconductors, mass-separated impurity introduction into ultra pure substrates is essential to avoid this strong optical (and corresponding electrical) compensation effect induced by oppositely charged impurities. Taking this conclusion into consideration, we emphasize that the optical properties of doped semiconductors should be totally re-examined in a more detailed and systematic manner.