Molecular beam epitaxy of GaBiAs on (311)B GaAs substrates

Abstract

We report the growth by molecular beam epitaxy of GaBi x As 1−x epilayers on ͑311͒B GaAs substrates. We use high-resolution x-ray diffraction ͑HRXRD͒, transmission electron microscopy, and Z-contrast imaging to characterize the structural properties of the as-grown material. We find that the incorporation of Bi into the GaBiAs alloy, as determined by HRXRD, is sizably larger in the ͑311͒B epilayers than in ͑001͒ epilayers, giving rise to reduced band-gap energies as obtained by optical transmission spectroscopy. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2827181͔ GaBi x As 1−x alloys are attracting in recent years a considerable deal of attention. [1][2][3][4][5][6] The band gap of GaAs is strongly reduced upon the addition of small amounts of Bi ͑ϳ90 meV per percent of Bi͒, with a strong enhancement of the spinorbit splitting energy.3,4 These remarkable properties make the Ga͑In͒BiAs system an attractive candidate to develop GaAs-based applications for long-wavelength optoelectronics as well as for spintronics. While the use of dilute nitrides in device applications is currently limited because the electron mobility of these compounds is abruptly reduced due to strong N-related alloy scattering, dilute bismides might exhibit improved transport properties. 6 The growth of epitaxial layers on high-index planes represents a step forward in semiconductor material engineering, as it offers an additional degree of freedom to develop applications with improved properties with respect to the conventional ͑001͒-grown devices. The interest in non-͑001͒ semiconductor structures is manifold and concerns growth, impurity incorporation, electronic properties, lasing performance, and piezoelectric effects. To mention a few examples, the use of non-͑001͒ substrates has allowed the fabrication of ultrahigh mobility two-dimensional hole gases in GaAs/ AlGaAs heterostructures, high-performance InAs/ GaAs quantum dot ͑QD͒ lasers, InGaAs/ GaAs QDs with enhanced piezoelectric effects, and GaMnAs epilayers with modified Mn incorporation and magnetic anisotropies. [7][8][9] In this study, we explore the growth by molecular beam epitaxy ͑MBE͒ of GaBiAs alloys on ͑311͒B GaAs substrates. We use a series of structural and optical techniques to characterize the as-grown material and to determine the amount of Bi incorporated into the samples. Our results reveal that the incorporation of Bi is enhanced in the ͑311͒B samples in comparison to the conventional ͑001͒ orientation.For this study, GaBi x As 1−x films were grown by MBE on semi-insulating ͑001͒ and ͑311͒B GaAs substrates at a growth temperature ͑T G ͒ of ϳ350°C with different As to Ga flux ratios. The growth was performed in a specially designed MBE reactor ͑see Ref. 10 for details͒. Atomic Ga and Bi were used as group-III and group-V sources, respectively, while As in the form of dimers ͑As 2 ͒ was produced by using a two-zone purpose made cell. In order to incorporate Bi efficiently into MBE-grown GaAs, the Ga to As flux needs to be on the brink of As shortage, close to...

Raman scattering reveals strong LO-phonon-hole-plasmon coupling in nominally undoped GaAsBi: optical determination of carrier concentration

“…Bi content was found by combining X-ray diffraction [18], energy-dispersive X-ray spectroscopy, and photoluminescence [19]. More details of the samples are given elsewhere [20].…”

Raman scattering studies of strain effects in (100) and (311)B GaAs1−xBix epitaxial layers

“…[1][2][3][4][5][6][7] This is because growers are currently confronted with some physical and technical issues that have thus far restricted the amount of Bi able to be introduced into the GaAs matrix. 8 The largest Bi incorporation experimentally reported has been x ¼ 0.22 for GaAs 1Àx Bi x films grown on bulk (100) GaAs substrate.…”

Polarized Raman backscattering selection rules for (hhl)-oriented diamond- and zincblende-type crystals

“…[2][3][4] This is largely due to the surface step structures exhibited by highindex crystal planes, which play an important role in the vapor-solid reaction processes and surface reconstruction. Certain surface reconstructions have been shown to affect the important mechanisms of epitaxial deposition 5 as well as the final bulk properties. 3 Studies of (hhl) crystal growths misoriented between (001) and (110) planes (see Fig.…”