GaAs-based Heterostructures Research Articles

Morphology transformations of GaAs high-index surfaces during the initial stages of strained-layer overgrowth

We study the initial stage of InAs and Si growth on GaAs (311) and (211). In situ reflection high-energy electron diffraction shows the morphology of these surfaces to transform from corrugated to flat during deposition of fractional InAs and Si monolayers. This result is confirmed by high resolution electron microscopy investigations of an InAs monolayer embedded in (311) GaAs showing perfectly flat heterointerfaces. Our findings negate the existence of lateral patterning effects due to the surface corrugation in strained, GaAs-based heterostructures with high-index orientation, but they simultaneously demonstrate a novel method to manipulate interfaces in semiconductor heterostructures.

Nonparabolicity effects on cyclotron mass in GaAs quantum wells.

Cyclotron-resonance measurements are reported on GaAs/(Ga,Al)As quantum wells of various thicknesses between 58 and 373 \AA{}. It is found that the cyclotron mass can be understood in terms of a parallel effective mass which is more enhanced by conduction-band nonparabolicity than the perpendicular mass, relevant for calculating the confinement energies. The measured cyclotron-resonance masses agree well with the theoretical approach of Ekenberg [Phys. Rev. B 40, 7714 (1989)]. This confirms the validity of describing band nonparabolicity in terms of a reliable energy-dependent effective mass that can be used to compute, e.g., shallow donor levels in GaAs-based heterostructures.

In-situ selective-area epitaxy of a GaAs-based heterostructure using a GaAs oxide layer as a mask

The in-situ selective-area epitaxy of InGaAs/GaAs was demonstrated by combining a GaAs oxide mask with metalorganic molecular beam epitaxy (MOMBE). All of the necessary processes for selective-area epitaxy were carried out in a MOMBE system without exposing the wafer to air. A mass spectrometric analysis of the decomposition of the source materials indicates that the surface-catalyzed decomposition of the source materials induces selective growth.

Transient hot-phonon effects on the velocity overshoot of GaAs: A Monte Carlo analysis

A novel ensemble Monte Carlo algorithm has been developed to simulate nonequilibrium phonon effects in the transient and steady-state high-field conductivity of bulk n-GaAs. The interplay of the electronic intervalley transfer with the mutual drag and heating between the carriers and longitudinal optical phonons is demonstrated over a wide range of fields, temperatures and carrier densities. For the moderately high doping levels of practical interest the characteristic times for a strong phonon amplification turn out to be sufficiently long to prevent a substantial interference of phonon disturbances with the onset of valley transfer during overshoot, but modifications of up to 20 percent are found for the steady-state velocity, with a gradual change from an enhancement at low fields to a comparable decrease around the maximum and negative differential part of the velocity-field characteristics. Comparable nonequilibrium-phonon effects are found for the case of negligible (i.e. remote) ionized-impurity scattering as realized in various GaAs-based heterostructures.

Growth and Characterization of GaAs-Based Heterostructures on Si By Mocvd

AbstractAbstract: Several different types of GaAs-AlGaAs heterostructures were grown on Si substrates by MOCVD. The defect density in as-grown samples (~108cm−2) was similar to that of GaAs layers grown directly on Si, and the crystalline quality of the material was observed to improve slightly with post-growth annealing at 900°C. We examined the diffusion of both Si and Zn dopants during this type of annealing and found only a small amount of redistribution of both species. Laser annealing of GaAs-on-Si was also examined as a method of reducing the defect density in the material - we observed substantial improvements in surface quality, but no change in sub-surface crystalline quality.