Effect of Substrate Orientation on the Growth Rate, Surface Morphology and Silicon Incorporation on GaSb Grown by Metal-Organic Vapor Phase Epitaxy

The growth and dopant incorporation during metal-organic vapor phase epitaxy (MOVPE) strongly depends on the orientation of the starting substrates. MOVPE of Si-doped GaSb layers on (100), (111)B and (111)A substrates were used to investigate the effect of orientation on the growth rate, the surface morphology and the silicon incorporation. orientation dependence of growth rates was studied as a function of temperature and V/III ratio. As the V/III ratios increases, the growth rate on the (111)B oriented substrate decreases, whereas that on the (111)A oriented substrate increases. The surface morphology on different substrates was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Flat-top hexagonal hillocks were observed on (111)B surface, and the growth was by step-flow on these facets. A surface kinetic growth model has been proposed to describe the growth features observed on (111)B surfaces. Finally, the orientation dependence of silicon incorporation was studied by secondary ion mass spectrometry (SIMS) and Hall measurements. It was found that the silicon incorporation rate was four times higher on (100) oriented surface than on (111)B oriented substrates. Although no conduction type switch was found on (111)B oriented substrate, throughout the Si doping range studied, a Ga slightly rich growth condition might be one of the factors accounting for the discrepancy between theoretical prediction and experimental results

Bias Selective Operation of Sb-Based Two-Color Photodetectors

Multicolor detectors have a strong potential to replace conventional single-color detectors in application dealing with the simultaneous detection of more than one wavelength. This will lead to the reduction of heavy and complex optical components now required for spectral discrimination for multi-wavelengths applications. This multicolor technology is simpler, lighter, compact and cheaper with respect to the single-color ones. In this paper, Sb-based two-color detectors fabrication and characterization are presented. The color separation is achieved by fabricating dual band pn junction on a GaSb substrate. The first band consists of an InGaAsSb pn junction for long wavelength detection, while the second band consists of a GaSb pn junction for shorter wavelength detection. Three metal contacts were deposited to access the individual junctions. Surface morphology of multi-layer thin films and also device characteristics of quasi-dual band photodetector were characterized using standard optical microscope and electro-optic techniques respectively. Dark current measurements illustrated the diode behavior of both lattice-matched detector bands. Spectral response measurements indicated either independent operation of both detectors simultaneously, or selective operation of one detector, by the polarity of the bias voltage, while serially accessing both devices

Continuous p-n junction with extremely low leakage current for micro- structured solid-state neutron detector applications

ABSTRACT Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as 10 B and 6 LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p + -n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p + -n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p + -Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p + -n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm 2 size were studied. A very low leakage current density of ~2×10 -8 A/cm 2 at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p + -n junction

Kinetics of Oxidation of Thiocyanate Ion by Iodamine-T in Perchloric Acid Medium

1149-115

Kinetics of Oxidation of Thiosemicarbazide by Iodamine-T, Iodine Monochloride & Iodine in Acid Medium

974-97

Ion-solvation studies of chloramine-T species in water, acetonitrile, DMF and their mixture by conductometry

1052-1055Transport property of the species of chloramine-T has been studied in water, acetonitrile, DMF and varying compositions (v/v) of water-acetonitrile, water-DMF mixtures and the data analysed by different conductivity models to identify the involvement of association process in the system. Limiting molar conductance has been found to be maximum in acetonitrile and minimum in DMF indicating the preferential solvation of cation by DMF. Association constant has been identified at all temperatures and compositions. Thermodynamic parameters have been estimated in all the cases. Viscosity of various solvents and solvent mixtures have been determined and used to compute Walden product from which Stoke's molecular radius is estimated. The ion-solvent and solvent-solvent interactions involved in the system have been qualitatively discussed

Kinetics & Mechanism of Oxidation of Thiocyanate Ion by Chloramine-B & Bromamine- B in Alkaline Medium

215-21

Effect of Metal Complexation on Kinetics & Mechanisms of Oxidation of Zn(II)-bound Thiosemicarbazide (TSC) by Chloramine-B (CAB) & Bromamine-B (BAB) in Aqueous Medium & by Dichloramine-B (DCB) in Aqueous Methanol

597-60

Electrical conductivity of Chloramine-B in water, acetonitrile, methanol and ethanol between 283-313 K

43-45<span style="font-size:11.0pt;line-height: 115%;font-family:Calibri;mso-fareast-font-family:" times="" new="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">Electrical conductance of Chloramine-B (CAB) in water, acetonitrile, methanol and ethanol has been studied between 283-313 K and was analyzed by Debye-Huckel-Onsager, Kraus-Bray and Shedlovsky conductivity equations. Molar conductance at infinite dilution, dissociation and association constants and Walden product are calculated at all temperature for all solvents. Energy of activation for the rate process and thermodynamic parameters have also been computed. Ionic conductance, ionic radius and transport number are theoretically calculated for CAB in water.</span