1.54 lm GaSb/AlGaSb multi-quantum-well monolithic laser at 77 K grown on miscut Si substrate using interfacial misfit arrays

A GaSb quantum-well (QW) laser diode grown monolithically on a 5deg miscut Si (001) substrate is presented. The III-Sb epi-structure is grown monolithically on the miscut Si substrate via a thin (50 nm) AlSb nucleation layer. The 13% lattice mismatch between AlSb and Si is accommodated by a self-assembled 2D array of interfacial misfit dislocations (IMF). The 5deg miscut geometry enables simultaneous IMF formation and anti-phase domain suppression. The 1 mm times 100 mum GaSb QW laser diode operates under pulsed conditions at 77 K with a threshold current density of 2 kA/cm² and a maximum peak power of ~20 mW. Furthermore, the device is characterised by a 9.1 Omega forward resistance and a leakage current density of 0.7 A/cm² at -5 V.     

Low threshold current operation of self-assembled InAs/GaAs quantum dot lasers by metal organic chemical vapour deposition

Low threshold current operation of self-assembled InAs/GaAs quantum dot lasers grown by metal organic chemical vapour deposition is reported. Continuous-wave lasing at room temperature with low threshold current (6.7 mA) was achieved at the wavelength of 1.18 /spl mu/m. The threshold current of 6.7 mA is the lowest value so far achieved in quantum dot lasers grown by metal organic chemical vapour deposition. Comparison with photoluminescence spectra indicates that the observed lasing originates from the ground state of InAs quantum dots.     

Alcohol modulation of single GABA(A) receptor-channel kinetics

Alcohol modulation of single-channel kinetics of GABA(A) receptor currents was studied with rat dorsal root ganglion neurons using the excised outside-out patch clamp technique. GABA (1 microM) alone or GABA (1 microM) plus ethanol (30-300 mM) or n-Octanol (30-300 microM) were applied by pressure ejection to evoke single-channel currents. The main single-channel conductance was not changed by either ethanol or n-Octanol at 25 pS. Both alcohols exerted the same effects on the single-channel kinetics, although n-Octanol was more potent than ethanol. The frequency of openings, the mean open time, the percentage of open time, the frequency of bursts, and the mean burst duration were all increased, but the mean closed time was decreased. These changes in channel kinetics account for the increase in whole-cell current amplitude caused by ethanol and n-Octanol.     

Time-resolved photoluminescence of type-II Ga(As)Sb/GaAs quantum dots embedded in an InGaAs quantum well

Optical properties and carrier dynamics in type-II Ga(As)Sb/GaAs quantum dots (QDs) embedded in an InGaAs quantum well (QW) are reported. A large blueshift of the photoluminescence (PL) peak is observed with increased excitation densities. This blueshift is due to the Coulomb interaction between physically separated electrons and holes characteristic of the type-II band alignment, along with a band-filling effect of electrons in the QW. Low-temperature (4?K) time-resolved PL measurements show a decay time of [Formula: see text]?ns from the transition between Ga(As)Sb QDs and InGaAs QW which is longer than that of the transition between Ga(As)Sb QDs and GaAs two-dimensional electron gas ([Formula: see text]?ns).     

Simplified rapid non-radioactive PCR-SSCP method applied to K-ras mutation analysis

A newly modified non-RI, PCR-SSCP method is presented and applied to K-ras analysis of colorectal tumors. It comprises five steps: (1) sampling of tiny pieces of fresh solid tissue by scraping with disposable bamboo combs (thin bars made of bamboo, 3 x 3 x 120 mm in size); (2) one-step DNA extraction with lysis buffer containing proteinase K, Nonidet P-40 and Tween 20; (3) PCR with 108 bp, c-ki-ras 2 gene primers; (4) SSCP analysis with 10% formamide-added polyacrylamide gels; and (5) detection with silver staining. In comparison with conventional RI- or non-RI-PCR-SSCP, It can give reliable and clear results in a much shorter time (within a total of 6 h). This novel approach should allow more frequent use of molecular diagnosis in biopsies and surgical pathology.     

Lateral interdot carrier transfer in an InAs quantum dot cluster grown on a pyramidal GaAs surface

InAs quantum dot clusters (QDCs), which consist of three closely spaced QDs, are formed on nano-facets of GaAs pyramidal structures by selective-area growth using metal-organic chemical vapor deposition. Photoluminescence (PL) and time-resolved PL (TRPL) experiments, measured in the PL linewidth, peak energy and QD emission dynamics indicate lateral carrier transfer within QDCs with an interdot carrier tunneling time of 910 ps under low excitation conditions. This study demonstrates the controlled formation of laterally coupled QDCs, providing a new approach to fabricate patterned QD molecules for optical computing applications.     

Room-Temperature Operation of Buffer-Free GaSb–AlGaSb Quantum-Well Diode Lasers Grown on a GaAs Platform Emitting at 1.65 μm

Buffer-free growth of GaSb on GaAs using interfacial misfit (IMF) layers may significantly improve the performance of antimonide-based emitters operating between 1.6 and 3 mum by integrating III-As and III-Sb materials. Using the IMF, we are able to demonstrate a GaSb-AlGaSb quantum-well laser grown on a GaAs substrate and emitting at 1.65 mum, the longest known operating wavelength for this type of device. The device operates in the pulsed mode at room temperature and shows 15-mW peak power at -10degC and shows high characteristic temperature (T_o) for an Sb-based active region. Further improvements to IMF formation can lead to high-performance lasers operating up to 3 mum.     

Improved photoluminescence efficiency of patterned quantum dots incorporating a dots-in-the-well structure

InAs quantum dots embedded in InGaAs quantum well (DWELL: dots-in-the-well) structures grown on nanopatterned GaAs pyramids and planar GaAs(001) surface are comparatively investigated. Photoluminescence (PL) measurements demonstrate that the DWELL structure grown on the GaAs pyramids exhibits a broad quantum well PL band (full width at half-maximum ～ 90?meV) and a higher quantum dot emission efficiency than the DWELL structure grown on the planar GaAs(001) substrate. These properties are attributed to the InGaAs quantum well with distributed thickness profile on the faceted GaAs pyramids, which introduces a tapered energy band structure and enhances carrier capture into the quantum dots.     

Device Characteristics of GaInSb/AlGaSb Quantum Well Lasers Monolithically Grown on GaAs Substrates by Using an Interfacial Misfit Array

We report the device characteristics of GaInSb/AlGaSb quantum well (QW) lasers monolithically grown on GaAs substrates by using an interfacial misfit (IMF) array. The IMF array localized at the GaSb/GaAs interface can accommodate the 7.8% lattice mismatch between GaAs substrates and GaSb buffer layers, resulting in the formation of a GaSb buffer with a very low defect density on GaAs substrates. Top-top and top-bottom metal contact methods are applied to the Ga_0.9In_0.1Sb/GaSb QW edge-emitting lasers monolithically grown on GaAs substrates for characterizing current–voltage (I–V) and output power–current (L–I) curves. The potential drop at the IMF array of ~0.7 V is elucidated by comparing I–V characteristics with these two contact methods. L–I characteristics and electroluminescence spectra shows room-temperature lasing at 1.83 μm from a 1.25-mm-long top-top contact device containing six-layer Ga_0.9In_0.1Sb QWs with a threshold current density (J _th) of 860 kA/cm². This IMF technique will enable a wide range of lasing wavelengths from near- to mid-wavelength infrared regimes on a GaAs platform.