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In this paper, GaSb nanostructures prepared under different Sb/background As ratios are investigated. With decreasing Sb/background As ratios, the morphologies of GaSb nanostructure changing from quantum dots (QDs) to quantum rings (QRs) are observed. The higher optical recombination probabilities of GaSb QRs are attributed to enhanced electron-hole wave function overlapping and more surrounding electrons around the GaSb QR core shell. With well-control Sb/background As ratios, the high-temperature operation GaSb quantum-dot infrared photodetector (QDIP) with simple stacked structure has been demonstrated. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The light-emitting diode (LED) with a single GaSb QD layer embedded in a GaAs n–i–p structure operated under different injection currents and temperatures is investigated. With increase in injection currents, room-temperature electroluminescence (EL) peak blue shift is observed until a saturation of EL intensity is reached. In the temperature-varying EL measurements, with increase in temperatures, EL peak blue shift and then red shift are observed, which is attributed to the enhanced luminescence of the smaller QDs with increase in temperatures lower than 100 K. The understanding of the operation mechanisms for the device is advantageous for the practical application of type-II LEDs.

The influence of As atoms on the morphologies of GaSb quantum dots (QDs) is investigated. Without any special treatment, GaSb quantum rings (QRs) are observed in the embedded GaSb layer even when the uncapped layer reveals QD like morphologies. With intentional As supply after the uncapped GaSb QD deposition, a QD to QR transition is observed. The phenomenon suggests that insufficient Sb atoms on the GaSb QDs would lead to the QD to QR transition as in the case of embedded GaSb layers. With extended Sb soaking time following GaSb deposition, QD structures could be well maintained for the embedded GaSb layers. A light-emitting diode operated at room temperature is fabricated based on the GaSb/GaAs QD structure. Identical peak positions in photoluminescence and electroluminescence (EL) spectra of the device show that type-II GaSb QDs are responsible for the observed EL.

The epitaxial growth of GaN on Si (111) substrates has been performed using plasma-assisted molecular beam epitaxy with a thin (∼19.3 nm) single-crystal layer of Sc 2 O 3 as a template/buffer layer. The structural properties and in situ epitaxial growth were studied using reflection high energy electron diffraction (RHEED), high-resolution transmission electron microscopy, and high-resolution X-ray diffraction. An orientation relationship of GaN(0 0 0 2)IISc 2 O 3 (111)∥Si(111) and GaN[1010]∥Sc 2 O 3 [422] off 60° with Si[422] was determined. The excellent growth of Sc 2 O 3 on Si and GaN on Sc 2 O 3 was achieved, as observed from streaky and bright RHEED patterns. The Sc 2 O 3 template serves as an effective barrier layer preventing diffusion of Si and Ga during the GaN growth at high temperatures under nitrogen plasma. No cracking was observed in the GaN layer with thickness around 0.2 μm when inspected with an optical microscope.

High κ Ga 2 O 3 (Gd 2 O 3 ) dielectric was deposited on n-type GaN (0 0 0 1) using molecular beam epitaxy (MBE). TiN/Ga 2 O 3 (Gd 2 O 3 )/GaN metal–oxide–semiconductor (MOS) diodes have exhibited a negligible frequency dispersion, low leakage currents (∼10 −8 A/cm 2 ), and a low interfacial density of states ( D it ) of 10 11 cm −2 eV −1 at the midgap. Well-behaved capacitance–voltage ( C V ) curves with accumulation and depletion behaviors were shown, with a dielectric constant of 14.7. Forming gas annealing at 600 °C has reduced the frequency dispersion in the C V curves. A sharp oxide/semiconductor interface was shown by high-resolution transmission electron microscopy (HR-TEM).

The influence of Sb/background As flux ratios on GaSb nano-structures is investigated in this letter. With decreasing Sb/background As flux ratios under high Sb irradiation during the post soaking procedure, ring formation, photoluminescence (PL) intensity enhancement, and PL peak red shift are observed. With further reduced Sb flux and Sb/background As ratios, the observed more intense PL intensities of the quantum-ring (QR) samples compared with quantum dots suggest that more electron-hole wave function overlapping is obtained. The observation of room-temperature electro-luminescence of a QR PIN diode has revealed the potential of the nano-structure in light-emitting device application.