Effect of pressure on defect-related emission in heavily silicon-doped GaAs

Abstract

We report cryogenic high-pressure measurements of a defect-related emission at 1.25 eV in silicon-doped GaAs. The pressure measurements prove that the 1.25-eV photon energy is relative to the conduction band, implying a deep defect level 0.30 eV above the valence band and an electron-capture process from the conduction band into the defect. The defect level moves up in the band gap at a rate of 23~3 meV/tGPa. These results are consistent with a vacancy-related defect level, possibly stemming from a gallium-vacancy -siliconat-gallium (second-nearest-neighbor) defect complex.Point defects occurring in semiconductors have been widely studied due to their technological relevance and because they pose numerous fundamental questions. Common to both issues is the position of defect-related levels introduced into the energy gap. In heavily doped semiconductors, the possibility that defect complexes that consist of native defects and substitutional dopant impurities exist in significant concentrations must be recognized. Identifying the microscopic defect origin of particular levels present in a semiconductor is an extremely challenging task. However, the study of plausible identifications of such defect signatures is important because any verifications facilitate examination and control of particular defect structures. %e present one such study in this paper.The experimental techniques used to explore these problems are diverse. Two important and related techniques which have been used fruitfully to investigate defects are spectroscopy under uniaxial stress ' and under hydrostatic pressure.Uniaxial stress measurements of defect-related states in GaAs are best used to break level degeneracies by lowering the symmetry of the defect, thereby splitting degenerate levels. Thc.~ain advantage of hydrostatic pressure as a means of perturbing a solid is that it isotropically decreases volume (i.e., interatomic spacing) in a bulk material. Shifts in energies are then due solely to the volume deformation induced by the pressure. In this paper we report on our use of hydrostatic pressure, in combination with low-temperature photoluminescence, to examine defect-related emission observed at 1.25 eV in heavily silicon-doped GaAs. ' ' The objectives were to determine the exact position of the level in the band gap (i.e., emission from the defect level to the valence band or from the conduction band to the defect level), and to provide information about the microscopic origin of this level.The silicon-doped GaAs was grown via molecular-beam epitaxy (MBE) at 580 'C. The GaAs:Si layer was grown on an undoped GaAs buffer layer that had been deposited on pure liquid-encapsulated Czochralski G~substr ates.Growth-layer thicknesses ranged from 2000 to 6500 A. Silicon concentratjons ranged from 3.9X 10 to 8.6X 10 cm, which we determined by Hall measurements and conGaAs:Si ethanol was used as a pressure-transmitting medium, and ruby was used to determine the pressure. ' All pressure changes were made at room temperature because previous cryogen...

Transformation of GaAs into an indirectL-band-gap semiconductor under uniaxial strain

“…15 and 16͒ spectra in diamond-anvil cells. Due to the technological importance of GaAs, the DIT was used to investigate various aspects of band-structure theory including the scattering cross sections of intraband transitions, 1,2 the formation of shallow impurities, [17][18][19] the nature and origin of the DX center, [20][21][22] and the dynamics of excited carriers. 23,24 Application of hydrostatic pressure to a cubic crystal causes the volume to decrease while preserving the crystal symmetry.…”

Photoluminescence upconversion atGaAs/InGaP2interfaces driven by a sequential two-photon absorption mechanism

“…1(a), close to the rear heterojunction. At lower energies, we observe a luminescence band centered on 1.214 eV, which is a common feature in n-type GaAs and can be ascribed to donor-acceptor type transitions where the acceptor level is formed by a Ga vacancy [32][33][34]. Since this luminescence band is associated with n-type material, we expect it to originate from the buffer layer and/or the substrate in our sample.…”

Cathodoluminescence characterization of Si-doped orientation patterned GaAs crystals

“…The spectrum of the Si-doped sample shows broadening, and blue shift of the NBE band, which can be associated with conduction band filling (Burstein Moss) (13). It presents three bands peaking at 901.8 nm (1.37 eV), which can be associated with V As acceptor complexes (14), a broad band peaking at 1010 nm (1.22 eV) henceforth labelled 1000 nm band, related to V Ga -Si Ga complex (15), and a second broad band peaking 1200 nm (1.03 eV) henceforth labelled 1200 nm band, this band is only observed in Si-doped samples, it is usually related to a complex involving Si impurities, Si Ga -Si As (16). In ref.…”