Gal(1-x)Mn(1-x)Sb grown on GaSb with mass-analyzed low-energy dual ion beam deposition

The Ga1-xMnxSb samples were fabricated by the implantation of Mn ions into GaSb (1 0 0) substrate with mass-analyzed low-energy dual ion beam deposition system, and post-annealing. Auger electron spectroscopy depth profile of the Ga1-xMnxSb samples showed that the Mn ions were successfully implanted into GaSb substrate. Clear double-crystal X-ray diffraction patterns of the Ga1-xMnxSb samples indicate that the Ga1-xMnxSb epilayers have the zinc-blende structure without detectable second phase. Magnetic hysteresis-loop of the Ga1-xMnxSb epilayers were obtained at room temperature (293 K) with alternating gradient magnetometry. (c) 2005 Elsevier B.V. All rights reserved.

Photoluminescence study of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum well grown by molecular beam epitaxy

Photoluminescence study of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum wells (BQWs) grown by molecular beam epitaxy (MBE) were carried out. Temperature and excitation power dependent photoluminescence (PL) study indicated that the band alignment of the BQWs is type - II. The origin of the double-peak luminescence was discussed. Under optimized growth conditions, the PL emission wavelength from the BQWs has been extend up to 1.31 mu m with a single peak at room temperature.

Electron beam and laser testing on the novel stripixel detectors

The novel Si stripixel detector, developed at BNL (Brookhaven National Laboratory), has been applied in the development of a prototype Si strip detector system for the PHENIX Upgrade at RHIC. The Si stripixel detector can generate X-Y two-dimensional (2D) position sensitivity with single-sided processing and readout. Test stripixel detectors with pitches of 85 and 560 mu m have been subjected to the electron beam test in a SEM set-up, and to the laser beam test in a lab test fixture with an X-Y-Z table for laser scanning. Test results have shown that the X and Y strips are well isolated from each other, and 2D position sensitivity has been well demonstrated in the novel stripixel detectors. (c) 2005 Elsevier B.V. All rights reserved.

Molecular beam epitaxy growth and photoluminescence study of room temperature 1.31 mu m (InyGa1-yAs/GaAs1-x Sb-x)/ GaAs bilayer quantum wells

Molecular beam epitaxy (MBE) growth of (InyGa1-yAs/GaAs1-xSbx)/GaAs bilayer quantum well (BQW) structures has been investigated. It is evidenced by photo luminescence (PL) that a strong blue shift of the PL peak energy of 47 meV with increasing PL excitation power from 0.63 to 20 mW was observed, indicating type II band alignment of the BQW. The emission wavelength at room temperature from (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW is longer (above 1.2 μ m) than that from InGaAs/GaAs and GaAsSb/GaAs SQW structures (1.1 μ m range), while the emission efficiency from the BQW structures is comparable to that of the SQW. Through optimizing growth conditions, we have obtained room temperature 1.31 μ m wavelength emission from the (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW. Our results have proved experimentally that the GaAs-based bilayer (InyGa1-yAs/GaAs1-xSbx)/GaAs quantum well is a useful structure for the fabrication of near-infrared wavelength optoelectronic devices. © 2005 Elsevier B.V. All rights reserved.

Room temperature 1.25 mu m emission from high indium content InxGa1-xAs/GaAs quantum wells grown by molecular beam epitaxy

Long-wavelength high indium content InxGa1-xAs/GaAs single/multi quantum wells (QWs) structures have been successfully grown by molecular beam epitaxy. It is evidenced by X-ray measurements that the critical thickness of the well width of InxGa1-xAs/GaAs QWs with an indium content x of 47.5% can be raised up to 7nm without strain relation. 1.25μ m photoluminescence (PL) emission is obtained from the QWs with narrower full-width at half maximum (FWHM) less than 30meV. Our results are important basements which are useful for further fabricating GaAs-based long-wavelength devices. © 2005 Elsevier B.V. All rights reserved.

In situ doping control for growth of n-p-n Si/SiGe/Si heterojunction bipolar transistor by gas source molecular beam epitaxy

N-p-n Si/SiGe/Si heterostructures have been grown by a disilane (Si2H6) gas and Ge solid sources molecular beam epitaxy system using phosphine (PH3) and diborane (B2H6) as n- and p-type in situ doping sources, respectively. Adopting an in situ doping control technology, the influence of background B dopant on the growth of n-Si emitter layer was reduced, and an abrupt B dopant distribution from SiGe base to Si emitter layer was obtained. Besides, higher n-type doping in the surface region of emitter to reduce the emitter resist can be realized, and it did not result in the drop of growth rate of Si emitter layer in this technology. (C) 2004 Elsevier B.V. All rights reserved.

Investigation of Mn-implanted n-Si by low-energy ion beam deposition

Mn ions were implanted to n-type Si(0 0 1) single crystal by low-energy ion beam deposition technique with an energy of 1000 eV and a dose of 7.5 x 10(17) cm(-2). The samples were held at room temperature and at 300degreesC during implantation. Auger electron spectroscopy depth profiles of samples indicate that the Mn ions reach deeper in the sample implanted at 300degreesC than in the sample implanted at room temperature. X-ray diffraction measurements show that the structure of the sample implanted at room temperature is amorphous while that of the sample implanted at 300degreesC is crystallized. There are no new phases found except silicon both in the two samples. Atomic force microscopy images of samples indicate that the sample implanted at 300degreesC has island-like humps that cover the sample surface while there is no such kind of characteristic in the sample implanted at room temperature. The magnetic properties of samples were investigated by alternating gradient magnetometer (AGM). The sample implanted at 300degreesC shows ferromagnetic behavior at room temperature. (C) 2004 Elsevier BN. All rights reserved.

A criterion for local interconvertibility between all-tripartite Gaussian states

We arrive at a necessary and sufficient criterion that can be readily used for interconvertibility between general, all-tripartite Gaussian states under local quantum operation. The derivation involves a systematic reduction that converts the original complex conditions in high-dimensional, 6n x 6n matrix space eventually into 2 x 2 matrix problems.

Fabrication of photonic crystals on several kinds of semiconductor materials by using focused-ion beam method

In this paper, we introduced the fabrication of photonic crystals on several kinds of semiconductor materials by using focused-ion beam machine, it shows that the method of focused-ion beam can fabricate two-dimensional photonic crystal and photonic crystal device efficiently, and the quality of the fabricated photonic crystal is high. Using the focused-ion beam method, we fabricate photonic crystal wavelength division multiplexer, and its characteristics are analyzed. (c) 2007 Elsevier B.V. All rights reserved.

Defects around self-organized InAs quantum dots measured by slow positron beam

Self-organized InAs quantum dots (QDs) have been fabricated by molecular beam epitaxy. The authors try to use a slow positron beam to detect defects in and around self-organized QDs, and point defects are observed in GaAs cap layer above QDs. For the self-organized InAs QDs without strain-reducing layer, it is free of defects. However, by introducing a strain-reducing layer, the density of point defects around larger sized InAs QDs increased. The above results suggest that low energy positron beam measurements may be a good approach to detect depth profiles of defects in QD materials. (c) 2007 American Institute of Physics.

Optimization of GaInNAs(Sb)/GaAs quantum wells at 1.3-1.55 mu m grown by molecular beam epitaxy

The InGaNAs(Sb)/(GaNAs)/GaAs quantum wells (QWs) emitting at 1.3-1.55 mu m have been grown by molecular beam epitaxy (MBE). The parameters of the radio frequency (RF) such as RF power and flow rate are optimized to reduce the damages from the ions or energetic species. The growth temperature is carefully controlled to prevent the phase segregation and strain relaxation. The effects of Sb on the wavelength and quality are investigated. The GaNAs barrier is used to extend the wavelength and reduce the strain. A 1.5865 mu m InGaNAs(Sb)/GaNAs SQW edge emitting laser lasing at room temperature at continuous wave operation mode is demonstrated. (c) 2006 Elsevier B.V. All rights reserved.

Metamorphic growth of 1.25-1.29 mu m InGaAs quantum well lasers on GaAs by molecular beam epitaxy

We demonstrate 1.25-1.29 mu m metamorphic laser diodes grown on GaAs by molecular beam epitaxy (MBE) using an alloy-graded buffer layer (GBL). Use of Be in the GBL is effective to reduce surface/interface roughness and improves optical quality. The RMS surface roughness of the optimized metamorphic laser is only two atomic monolayers for 1 x 1 mu m(2). Cross-sectional transmission electron microscopy (TEM) images confirm that most dislocations are blocked in the GBL. Ridge waveguide lasers with 4 mu m wide ridge were fabricated and characterized. The average threshold current under the pulsed excitation is in 170-200 mA for a cavity length of 0.9-1.5 mm. This value can be further reduced to about 100 mA by high-reflectivity coating. Lasers can work in an ambient temperature up to at least 50 degrees C. (c) 2006 Elsevier B.V. All rights reserved.

Application of rapid thermal annealing on 1.3-1.55 mu m GaInNAs(Sb) lasers grown by molecular beam epitaxy

Rapid thermal annealing (RTA) has been demonstrated as an effective way to improve the crystal quality of GaInNAs(Sb) quantum wells (QWs). However, few investigations have been made into its application in laser growth and fabrication. We have fabricated 1.3 mu m GaInNAs lasers, both as -grown and with post-growth RTA. Enhanced photoluminescence (PL) intensity and decreased threshold current are obtained with RTA, but the characteristic temperature T-o and slope efficiency deteriorate. Furthermore, T-o has an abnormal dependence on the cavity length. We attribute these problems to the deterioration of the wafer's surface. RTA with deposition Of SiO2 was performed to avoid this deterioration, T-o was improved over the samples that underwent RTA without SiO2. Post-growth and in situ annealing were also investigated in a 1.55 mu m GaInNAsSb system. Finally, continuous operation at room temperature of a GaAs-based dilute nitride laser with a wavelength over 1.55 mu m was realized by introducing an in situ annealing process. (c) 2007 Elsevier B.V. All rights reserved.

Evolution of InAs/GaAs(001) islands during the two- to three-dimensional growth mode transition in molecular-beam epitaxy

A detailed observation was made using atomic force microscopy on the two- to three-dimensional (2D-3D) growth mode transition in the molecular-beam epitaxy of InAs/GaAs(001). The evolution of the 3D InAs islands during the 2D-3D mode transition was divided into two successive phases. The first phase may be explained in terms of a critical phenomenon of the second-order phase transition.

Growth of GaSb layers on GaAs (001) substrate by molecular beam epitaxy

GaSb 1 mu m-thick layers were grown by molecular beam epitaxy on GaAs (001). The effects of the growth conditions on the crystalline quality, surface morphology, electrical properties and optical properties were studied by double crystalline x-ray diffraction, atomic force microscopy, Hall measurement and photoluminescence spectroscopy, respectively. It was found that the surface roughness and hole mobility are highly dependent on the antimony-to-gallium flux ratios and growth temperatures. The crystalline quality, electrical properties and optical properties of GaSb layers were also studied as functions of growth rate, and it was found that a suitably low growth rate is beneficial for the crystalline quality and electrical and optical properties. Better crystal quality GaSb layers with a minimum root mean square surface roughness of 0.1 nm and good optical properties were obtained at a growth rate of 0.25 mu m h(-1).