Infrared absorption and lowtemperature photoluminescence spectra of GaAs grown by molecular beam epitaxy Appl. Phys. Lett. 45, 922 (1984); 10.1063/1.95461 Effects of very low growth rates on GaAs grown by molecular beam epitaxy at low substrate temperatures ~e incorporation mechanisms of residual impurities in GaAs layers grown by molecular-beam epItaxy h.as been investigated by high-resolution photoluminescence (PL) spectroscopy at 2 K. A systematIc study of near-band-edge emissions of undoped GaAs layers grown at a wide range of growth temperatures (Tg), 47c}-750 ·C, demonstrates that PL spectra related with residual impurit~es ~e sign~ficantly dependent upon T g • It was found that maximum emission intensity of free exciton IS obtamed at Tg -550 ·C, and the minimum impurity incorporation is established at Tg of 550-650 .c.

Very dilute C+ (carbon) ion implantations were carried out for extremely pure GaAs wafers grown by molecular beam epitaxy (MBE). Low-temperature photoluminescence measurements revealed that at least five sharp new emission lines are commonly formed near bound exciton emission region by the introduction of C for the dose range between 1015 and 1017 cm−3. It was for the first time demonstrated that the most dominant line among the above emission is identical to the g line in defect-induced bound exciton emission series which are frequently observed in rather impure MBE-grown or metalorganic chemical vapor deposition (MOCVD)-grown GaAs samples.

A drastic change of the conduction type from p to n with an increase of the As4 to Ga flux ratio, γ, was observed for the first time in the photoluminescence spectra of amphoteric impurity (Ge)-doped GaAs made by molecular-beam epitaxy. The sample with the lowest γ (γ=1.0) presented a purely p-type emission associated with pairs between the excited states of acceptors. The sample with the highest γ (γ=10.6) indicated a totally n-type emission reflecting an increase of quasi Fermi energy. Results show that by precisely controlling the flux ratio, γ, one can reliably make use of substantially amphoteric atoms of Ge both as p- and n-type impurities for the fabrication of GaAs by molecular-beam epitaxy.

Conditions for the formation of defect-induced bound exciton (DIBE) emissions in GaAs were investigated by molecular beam epitaxial method. Growth was made on both A- and B-polarity substrates with (321), (221), and (211) orientations. For A-polarity samples, (321)A and (211)A presented pronounced DIBE emissions. (221)A, however, exhibited no DIBE emission, instead it presented a dominant carbon donor-carbon acceptor pair emission together with a small hump due to carbon donor-related bound exciton emissions. For B-polarity specimens, DIBE was completely vanished in all the three samples. It was theoretically demonstrated that DIBE is formed only when double-handed Ga adatom site is existing.

Photoacoustic (PA) spectra near the energy gap of n- and p-type silicon were investigated at various carrier concentrations. The PA signal intensity at energies lower than the energy gap increased with increasing carrier concentration for both types. The increase is considered to be due to the increase in the heat generated in the samples following free carrier absorption and nonradiative relaxation processes. The PA signal intensity increased drastically above a carrier concentration of 1017 cm-3 for n-type and above that of 1016 cm-3 for p-type silicon.