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Hall characterization of epitaxial GaSb and AlGaAsSb layers using p-n junctions on GaSb substrates

: Predan, F.; Ohlmann, J.; Mrabet, S.; Dimroth, F.; Lackner, D.


Journal of Crystal Growth 496-497 (2018), pp.36-42
ISSN: 0022-0248
Journal Article
Fraunhofer ISE ()
Photovoltaik; III-V und Konzentrator-Photovoltaik; III-V Epitaxie und Solarzellen

The Hall Van-der-Pauw method is widely used to assess the electrical properties of GaSb based semiconductor layers. Semi-insulating GaSb substrates are not available, and therefore, Hall structures are generally grown on semi-insulating GaAs. The lattice mismatch of 7.8% between GaAs and GaSb results in high defect densities, which may influence the measurement. We investigated an alternative approach for Hall effect measurements using a p-n junction for the electrical isolation of the test layer from layers below. This allows antimonide based test layers with low defect density grown lattice-matched on GaSb substrates to be analyzed. Negligible leakage currents across the p-n junctions are key to ensure significant measurement results. n- and p-GaSb layers show similar carrier concentration if grown on GaSb or semi-insulating GaAs, with the exception of highly n-doped layers >5 x 1017 cm−3. However, majority carrier mobilities were systematically higher on GaSb substrate, explained by a lower density of structural defects. Furthermore, the sample design with p-n junction enabled Hall effect measurements of quaternary p-Al0.2Ga0.8As0.02Sb0.98 layers, which was impossible for those same layers grown on GaAs due to strain induced phase-separation. The methodology is presented for antimonides, but it is applicable to a wide range of material systems including metamorphic structures.