Deep-level defects in n-type GaAsBi alloys grown by molecular beam epitaxy at low temperature and their influence on optical properties

Abstract

Deep-level defects in n-type GaAs1−xBix having 0 ≤ x ≤ 0.023 grown on GaAs by molecular beam epitaxy at substrate temperature of 378 °C have been injvestigated by deep level transient spectroscopy. The optical properties of the layers have been studied by contactless electroreflectance and photoluminescence. We find that incorporating Bi suppresses the formation of GaAs-like electron traps, thus reducing the total trap concentration in dilute GaAsBi layers by over two orders of magnitude compared to GaAs grown under the same conditions. In order to distinguish between Bi- and host-related traps and to identify their possible origin, we used the GaAsBi band gap diagram to correlate their activation energies in samples with different Bi contents. This approach was recently successfully applied for the identification of electron traps in n-type GaAs1−xNx and assumes that the activation energy of electron traps decreases with the Bi (or N)-related downward shift of the conduction band. On the basis of this diagram and under the support of recent theoretical calculations, at least two Bi-related traps were revealed and associated with Bi pair defects, i.e. (VGa+BiGa)−/2− and (AsGa+BiGa)0/1−. In the present work it is shown that these defects also influence the photoluminescence properties of GaAsBi alloys.

A comparative study of epitaxial InGaAsBi/InP structures using Rutherford backscattering spectrometry, X-ray diffraction and photoluminescence techniques

“…However, given that there was little evidence of bismuth incorporation from XRD, the origin of the long wavelength emission is uncertain in this sample. It may be caused by various reasons including possible localised states with strong PL signal at longer wavelengths at low temperature [5] and/or recombination via defect related traps [19] caused by the low growth temperature. We make a note of caution here that such long-wavelength emission bands may also relate to the low-temperature grown InGaAs layer of the cap as we recently observed in This is the author's peer reviewed, accepted manuscript.…”

“…This sample exhibited very strong broad low temperature PL in spectral range 1750-2800nm, which indicated the presence of localised states. We cannot rule out the possibility of recombination via defect related traps either in InGaAsBi layer itself [19] or This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.…”

Atomic-Resolution EDX, HAADF, and EELS Study of GaAs1-xBix Alloys

“…Low temperatures needed to incorporate larger concentrations of Bi make molecular-beam epitaxy (MBE) the preferred method of synthesis, although progress has been made using metal-organic vapour phase-epitaxy [15][16][17]. GaAsBi alloys still show surprisingly high photoluminescence (PL) intensity for these low growth temperatures, which is attributed to the Bi surfactant effect and reduced density of As-related point defects that typically form in low-temperature GaAs [18,19]. In the picture of the valence band (VB) anti-crossing, incorporated individual Bi atoms produce a resonant state below the extended GaAs VB causing the optical band gap reduction [2,20,21].…”

Type I GaSb1-xBix/GaSb quantum wells dedicated for mid infrared laser applications: Photoreflectance studies of bandgap alignment

“…Moreover, GaSbBi alloys have not been explored much, in contrast to GaAsBi alloys, which have been extensively studied in recent years by several groups. [14][15][16][17][18][19][20][21][22][23][24] In the case of GaAsBi, it is observed that Bi tends to segregate toward the surface and to form droplets due to its large size in comparison with arsenic. Therefore, the growth of III-V-Bi materials is usually achieved using very-low growth temperatures and a near stoichiometric V/III ratio.…”

“…Such conditions usually favor the formation of point defects, which are sources of deep levels and nonradiative recombination in this material system. 24 Compared to GaAsBi, the situation in GaSbBi can be different due to the smaller difference between the group V atoms in terms of their electronegativities and sizes. As shown in Ref.…”