Lambkin Jd

Thermal quenching of the photoluminescence of InGaAs/GaAs and InGaAs/AlGaAs strained‐layer quantum wells

Photoluminescence in InGaAs/GaAs strained‐layer quantum wells is strongly quenched by temperatures above 10–100 K, depending on the well width. Analysis of this dependence shows that the quenching mechanism is thermal activation of electron‐hole pairs from the wells into the GaAs barriers, followed by nonradiative recombination through a loss mechanism in bulk GaAs. The addition of Al to the barriers to improve confinement eliminates loss through this route but introduces another loss mechanism, characterized by an activation energy independent of well width and with a smaller pre‐exponential factor.

A photoluminescence study of indium desorption from strained Ga1−xInxAs/GaAs

Abstract In this paper we present detailed measurements of the thermal desorption rates of indium from strained GaInAs grown off a GaAs substrate. We have made these measurements by monitoring the photoluminescence (PL) of the groundstate emission from strained quantum wells. We show that this method can be an accurate and highly sensitive technique for measuring desorption rates. The measurements have been made as a function of composition and arsenic overpressure. A simple model for the indium incorporation is developed and an activation energy for the desorption process has been obtained.

Growth and characterization of relaxed epilayers of InGaAs on GaAs

Abstract We report the growth of 3 μm thick relaxed layers of In x Ga 1− x As on GaAs substrates, with x from 0.1 to 1, and give some results of compositional, optical, structural and electrical characterisation. Compositions were determined by several techniques, with results which agreed to within a Δx of ±0.02. For x above 0.2 the crystal quality is very poor. Some layers have been grown with stepped compositions up to x = 0.4 and this improves the crystal quality. We show that in the InGaAs/GaAs system there is a threshold strain, rather than threshold composition change, above which crystal quality is degraded.

The pressure dependence of the band offsets in a GaInAs/InP multiple quantum well structure

Abstract The photoluminescence of a GaInAs/InP quantum well structure grown by MOCVD has been measured up to 70 kbar using a miniature cryogenic diamond anvil cell. Together with measurements of the bulk material, these data determine the pressure dependence of the confinement energies. It is found that the confinement energies decrease with pressure, and that the effect is more marked in narrow wells. In order to explain these results in terms of the pressure dependence of the barrier heights, effective masses, and well widths, it is found necessary to include a pressure dependence of the band offset. We find that the valence band offset is virtually independent of pressure while the conduction band offset decreases by approximately 2.3±0.6 meV/kbar. This is approximately the difference in pressure coefficients of the direct band-gaps of GaInAs and InP.

A portable high-pressure system for low-temperature optical and transport measurements

A low-temperature hydraulic high-pressure cell is described. It provides the capability of electrical and optical measurements to 800 MPa at 4 K, and with its diameter of 19 mm will fit most commercial cryostats. A portable intensifier has been developed to supply the pressure fluid.

The hydrostatic pressure dependence of the band-edge photoluminescence of GaInAs

Abstract The hydrostatic pressure dependence of the band gap of a GaInAs epilayer has been measured by photoluminescence in a diamond anvil cell at room temperature and 80 K. The initial pressure coefficient of the band-gap is found within experimental error to be independent of temperature with a value of 10.95 ± 0.1 meV kbar-1. The dependence of the band gap on lattice constant is found to be linear, described by a deformation potential of -8.25 ± 0.1 eV for a bulk modulus of 760kbar.

The pressure dependence of the valence band discontinuity in quantum well structures

The use of hydrostatic pressure to determine the valence and conduction band offsets and their pressure dependence in both Type I and Type II quantum well structures will be described. Recent exper...

Photoluminescence of InGaAs/GaAs strained-layer quantum well structures under high pressure

Abstract Measurements of the photoluminescence (PL) of strained In0.2Ga0.8As/GaAs and In0.15Ga0.85As/GaAs quantum well structures together with the PL from bulk GaAs, in a diamond anvil cell show that the pressure coefficient of the ground confined state in the wells depends upon well width (LZ). In the thinnest wells, the coefficient is closer to that of the bulk GaAs (10.7 meV/kbar), as expected. However, in the widest wells the coefficients tend to values (9.5meV/kbar for the 15% alloy and 9.1meV/kbar for the 20% alloy) that are significantly lower than the pressure coefficient of unstrained In0.53Ga0.47As (10.9meV/kbar). It is found that the low pressure coefficients can not be explained by the change in uniaxial stress with pressure due to a difference in bulk moduli between the barrier and well.