We have applied positron annihilation spectroscopy to study native point defects in Te-doped n-type and nominally undoped p-type GaSb single crystals. The results show that the dominant vacancy defect trapping positrons in bulk GaSb is the gallium monovacancy. The temperature dependence of the average positron lifetime in both p- and n-type GaSb indicates that negative ion type defects with no associated open volume compete with the Ga vacancies. Based on comparison with theoretical predictions, these negative ions are identified as Ga antisites. The concentrations of these negatively charged defects exceed the Ga vacancy concentrations nearly by an order of magnitude. We conclude that the Ga antisite is the native defect responsible for p-type conductivity in GaSb single crystals.

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Native point defects in GaSb

GaSb nanowires were synthesized on c-plane sapphire substrates by gold-mediated vapor–liquid–solid (VLS) growth using a metalorganic chemical vapor deposition process. A narrow process window for GaSb nanowire growth was identified. Chemical analysis revealed variations in the catalyst composition which were explained in terms of the Au-Ga-Sb ternary phase diagram and suggest that the VLS growth mechanism was responsible for the nanowire growth. The nominally undoped GaSb nanowires were determined to be p-type with resistivity on the order of 0.23 Ω cm. The photoluminescence was found to be highly dependent on the V/III ratio, with an optimal ratio of unity.

Growth and characterization of unintentionally doped GaSb nanowires

Graded interface layers are commonly known to reduce the electrical series resistance of distributed Bragg-reflectors in vertical-cavity surface-emitting lasers in various material systems such as AlAs/GaAs or AlInAs/GaInAs. As these materials can be highly n-doped using silicon, a further decrease of the resistivity is easily achieved. However, for n-type GaSb/AlAsSb distributed Bragg reflectors on GaSb-substrates the free electron density due to doping in graded layers is reduced depending on the aluminum content and therefore optimized structures are hard to design. In this paper, we present electrical measurements on various grading and doping schemes, yielding a low-resistive interface suitable for application in mid-infrared vertical-cavity surface-emitting lasers.

Reduction of hetero-interface resistivity in n-type AlAsSb/GaSb distributed Bragg reflectors

Optical properties improvement of GaSb epilayers through defects compensation via doping

The authors are grateful for financial support from the State of Bavaria, the German Ministry of Education and Research (BMBF) via the national project HIRT (Grant No. FKZ 13XP5003B).

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B.F. Su

Papers

Gallium antisite defect and residual acceptors in undoped GaSb

Interface reaction of U3Si2-UO2 composite pellets during spark plasma sintering

Effect of annealing temperature on electronic band structural, optical constant, and band gap of uranium dioxide films

Role of martensitic interface on the discontinuous precipitation of U-Ti alloys at 400 ºC

Densification mechanism of U3Si2 consolidated by spark plasma sintering