K. Uchida

Pressure‐induced Γ‐X crossover in the conduction band of ordered and disordered GaInP alloys

Pressure‐dependent photoluminescence in both ordered and disordered Ga0.5In0.5P is reported. In ordered Ga0.5In0.5P, emissions are observed from both the direct band gap at the Brillouin zone center (Γ) and from the indirect band gap involving the conduction band at the X point of the Brillouin zone. The conduction‐band minima at X and Γ in the ordered phase are found to be lowered in energy by the same amount with respect to those in the disordered phase. Our results support the existence of ordering along the [001] direction in GaInP as proposed recently by Kurtz.

BAND ALIGNMENTS IN GAINP/GAP/GAAS/GAP/GAINP QUANTUM WELLS

Pressure-dependent photoluminescence (PL) in several GaInP(ordered)-GaAs quantum well structures grown by metal organic vapor phase epitaxy is reported. Quantum well emission from GaAs is observed only in structures where thin (∼2u2009nm) GaP layers are inserted between the GaAs well and the GaInP barrier. By extrapolating the energies of the various inter and intralayer PL transitions observed under pressures (up to 5.5 GPa) to zero pressure, the different band offsets of the heterostructure have been determined.

Comparative study of photoluminescence in ordered and disordered GaInP alloys under high pressure

Abstract We have measured the photoluminescence (PL) spectra of ordered and disordered Ga 0.5 In 0.5 P alloys grown by metalorganic vapor phase epitaxy under pressures from 0 to 6 GPa at three different temperatures ( T = 12, 77 and 300 K). At atmospheric pressure, the band-gap energy E 0 , derived from the PL spectrum, of the ordered GaInP is about 70 meV lower than that of the disordered alloy. With increasing pressure the PL spectrum exhibits a rapid shift toward higher energies. The band-gap energy E 0 of the ordered GaInP shows a sublinear pressure dependence up to about 4 GPa, while that of the disordered alloy increases almost linearly up to the highest pressures (3.0–3.5 GPa) beyond which the PL emission disappears. At lower temperatures ( T = 12 and 77 K) the PL peak energy for the ordered GaInP is also found to decrease in energy for pressures above 4 GPa. These results can be partly related to the existence of the repulsion between the Γ-folded energy states in the CuPt-type ordered structure, which affects E 0 and also the Γ - X crossover under high pressure in these materials.

Hydrostatic Pressure Dependence of Eg-100 meV Photoluminescence Emissions in n-Type AlGaAs

The pressure dependence of deep emission bands (occurring at about 100 meV below the band-to-band recombination peak) in two types of n-AlGaAs materials grown by Metal Organic Vapor Phase Epitaxy (MOVPE) and Molecular Beam Epitaxy (MBE) has been measured by Photoluminescence (PL) in order to investigate the origin of these deep emissions. The results indicate that these deep emissions are probably due to transition between a shallow donor and a deep accepter located about 100 meV above the valence band.

Photoluminescence of deep levels induced by sup-ppm H2O in AlGaAs grown by MOVPE

Abstract A photoluminescence (PL) peak has sometimes been observed at about 100 meV below the band edge emission in MOVPE grown n - Al x Ga − x As : ( Se and Si ) (0≦ x ≦0.3). It was studied in samples grown in the presence of H 2 O of 30–500 ppb. The dee level emission intensity ( I D ) at 77K was proportional to the H 2 O concentration (P H 2 O ) in the growth ambient. I D decreased a the growth temperature was increased. The oxygen concentrations in the epilayers were measured by a SIMS technique, and tended to follow the variation of I D , however, the correlation was not direct. The energy position of the peak nearly followed the variation of the Γ band as a function of the Al contents. But the peak was not observed for epi-GaAs. The intensity of deep-level emission tended to saturate and its position was shifted towards higher energies as the excitation power density was raised. Our results suggest that this deep-level emission comes from a distant pair transition between a shallow donor and a deep acceptor induced by the presence of sub-ppm H 2 O in the MOVPE growth ambient.