Growth and characterization of p-type As heterostructures grown on high-index GaAs surfaces

Autor: R. K. Hayden, Laurence Eaves, P.J. Rodgers, Paul Crump, B. L. Gallagher, Mohamed Henini
Rok vydání: 1995
Předmět:
Zdroj: Thin Solid Films. 267:106-113
ISSN: 0040-6090
DOI: 10.1016/0040-6090(95)06595-4
Popis: We have investigated a series of Be-doped GaAs (AlGa) As two-dimensional hole gas (2DHG) structures grown on (110)-, (111)B-, (211)B- and (311)B-orientated substrates and compare their properties with high-mobility samples grown on (311) A using Si doping. The samples were prepared and grown under the same conditions so as to render them comparable. They are found to have mobilities which are strongly anisotropic within the plane. The highest mobility, ∼ 100 000 cm2V−1s−1, for the Be-doped samples is found on the (110) surface while the (211) surface gave the lowest values, ∼ 10 000 cm2V−1s−1. However, the latter samples are found to have quantum Hall effect critical currents of > 70 μA, an exceptionally high value for a hole gas which makes them suitable for metrology. All the samples show strong low-field positive magnetoresistance with resistance increases of up to 30% at magnetic fields of only 0.1 T. The presence of this feature on all the different planes shows that it does not depend upon the details of the band structure. It is identified with the lifting of the degeneracy of the spin sub-bands by the asymmetrical potential giving rise to a classical two-band magnetoresistance. The modulation-doped GaAs (AlGa) As heterostructures on the (311) A GaAs surface using silicon as the acceptor produced 2DHGs with a low-temperature hole mobility exceeding 1.2 × 106 cm2 V−1 s−1 at carrier concentrations as low as 0.8 × 1011 cm−2. This hole mobility is the highest ever observed at such low densities by any growth technique. These 2DHG samples show for the first time the persistent photoconductivity effect. This effect is normally absent in 2DHG systems. An analysis of the number density and temperature dependence of the mobility leads us to conclude that the mobility is limited by phonon scattering above ~ 4 K and by interface scattering at lower temperatures. Continuous magnetic fields applied parallel to layer interfaces are used to examine the in-plane energy dispersion and anisotropy of the quantum well states in p-type silicon-doped double-barrier GaAs AlAs resonant tunnelling structures grown on the (311) A GaAs surface. Measurements reveal that the lowest subband is isotropic at low energies. This indicates that atomic layer corrugations may be important in determining the mobility of hole heterostructure devices grown on non-(100)-oriented surfaces.
Databáze: OpenAIRE
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