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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. [ABSTRACT FROM PUBLISHER]

This letter presents the lasing properties of InAs/GaAs quantum dot lasers with InGaP cladding layers grown by solid-source molecular-beam epitaxy. These Al-free lasers exhibit a threshold current density of 138 A/cm[sup 2], an internal loss of 1.35 cm[sup -1], and an internal quantum efficiency of 31% at room temperature. At a low temperature, a very high characteristic temperature of 425 K and very low threshold current density of 30 A/cm[sup 2] are measured. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: 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 100K. The understanding of the operation mechanisms for the device is advantageous for the practical application of type-II LEDs. [Copyright &y& Elsevier]