Reduction in sidewall recombination velocity by selective disordering in GaAs/AlGaAs quantum well mesa structures

Abstract

Sidewall recombination in SiO2-capped GaAs/AlGaAs multiple quantum well mesa structures is investigated using a time-resolved photoluminescence technique. Nonradiative recombination lifetimes in annealed samples are improved significantly compared with those in samples which are not annealed. This effect contributes to a reduction in sidewall recombination velocity due to disordering of quantum wells at the sidewall by cap annealing. Numerical analysis is used to fit the experimentally observed sample size dependence of the nonradiative lifetimes to calculated curves. This shows that the effective sidewall recombination velocity is reduced from 8×106 to 4×104 cm/s.

Dry etching and consequent burring regrowth of nanosize quantum wells stripes using an in situ ultrahigh vacuum multichamber system

“…PL intensity rapidly decreased with decreases in stripe width for as-etched wafers, which is the same as findings previously reported. 6 However, ex situ regrowth using solidsource MBE with H 2 SO 4 treatment, allowed the slope to decrease. This means that surface recombination was depressed by epipassivation.…”

“…The lifetime of excited carrier was measured for different stripe widths. In this stripe structure, is connected to stripe width w as follows: 6 1/ϭ1/ b ϩ2S v /w. b : nonradiative lifetime of the unpatterned sample.…”

“…However, it is well known that InGaAs͑P͒/InP has a much lower surface recombination velocity. 6 Therefore, we also fabricated InGaAs/InP wafers to examine the differences in quality between in situ regrown GaAs/AlGaAs wafers and ex situ regrown InGaAs/InP wafers. However, a simple comparison is not the sole purpose of this article but rather finding optimum ways of obtaining good-quality micro-or nanometer structures.…”

Diameter-dependent optical losses in pillar microcavities

“…This is because a reduction of carrier lifetime due to surface recombination or large optical losses in the cavity due to insufficient cavity structure raises the threshold current density. Although a quantitative characterization of surface recombination by time-resolved photoluminescence has been done, 6 no direct observation of the optical losses in a microcavity has been reported. When the cavity diameter is reduced to a few m, it is supposed that the optical loss is dominated by scattering losses on the cavity sidewall with process-induced microroughness.…”

Reduced nonradiative recombination in etched/regrown AlGaAs/GaAs structures fabricated by in situ processing

“…In these fine structures, however, when the surface of the fabricated active region is exposed to air, the resulting surface states easily cause carrier loss even if process-induced damage is completely removed. Hamao et al 8 found that when using flat AlGaAs/GaAs interfaces, in situ sample manipulation in an UHV environment restrained increase in nonradiative carrier recombination velocity, S, which severely occurred in the ex situ process. [1][2][3] In this context, in situ processing, where dry etching and crystal overgrowth are successively performed under ultrahigh vacuum ͑UHV͒ condition, is expected to provide processed/regrown interfaces with excellent quality owing to avoiding air-related contamination.…”