Surface doping of GaxIn1−xAs semiconductor crystals with magnesium
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Effects of magnesium (Mg) alloying of GaxIn1−xAs(100) semiconductor surfaces have been investigated by low-energy electron diffraction, scanning tunneling microscopy/spectroscopy, and responsivity analysis of an infrared-detector component. In particular, the formation of an unusual Mg-induced (2 × 1) structure on GaAs(100) surfaces is found when depositing 1–3 monolayers of Mg on a cleaned GaAs(100) surface followed by annealing the sample in vacuum conditions at up to 500 °C. Concomitantly, the spectroscopy data show that the Fermi-level shifts toward valence band at the surface, indicating p-type doping of a surface part of GaAs due to Mg incorporation into the semiconductor. This surface-doping effect is also present in a test GaxIn1−xAs infrared detector, leading to increase in the detector responsivity. This beneficial effect of Mg-induced p-type doping is explained by a band-bending induced transfer of electrons away from a defect-rich top interface.