摘要:

Measurements of the electron density in dc and pulsed silane/helium discharges show that the addition of silane to the gas mixture causes a large reduction in the electron density. By monitoring the electron decay time in the afterglow, it is found that the dominant electron loss mechanism in silane/helium is not ambipolar diffusion to the walls, but instead is a volumetric loss process, most likely dissociative attachment of electrons to a product of the silane dissociation. A lower bound for the rate coefficient for this loss process has been determined to be 2.65×10−10cm3/sec.

ISSN:0021-8979    

DOI:10.1063/1.336105

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The deposition of CdTe films on foreign substrates by the direct combination of the elements in a gasflow system has the flexibility that the conductivity type and electrical resistivity of the film can be controlled by adjusting the composition of the reaction mixture. The deposition and properties ofp‐type CdTe films are emphasized in this paper because of its importance in thin‐film solar cells. Graphite, W/graphite, mullite, and Corning 7059 glass were used as substrates for the deposition process. While CdTe films deposited on W/graphite and mullite substrates could benorptype, depending on the composition of the reaction mixture, all films deposited on graphite substrates wereptype, irrespective of the reactant composition, substrate temperature, or the purification of graphite, suggesting that carbon is electrically active in CdTe. The resistivity ofp‐type CdTe films on W/graphite and mullite substrates has been controlled for the first time by (1) using a Cd‐deficient reaction mixture, and (2) adding dopants (AsH3or PH3) to the reaction mixture. The resistivity versus composition relation was studied in detail. The optical properties of nearly stoichiometric, Cd‐deficient and Te‐deficient CdTe films were also investigated.

ISSN:0021-8979    

DOI:10.1063/1.336106

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The formation mechanism of drawing‐inducedE’centers in silica optical fibers is clarified by analyzing the thermodynamic behavior of point defects during the drawing process. TheE’center concentration in the fibers is given bynd=np exp(−Ef/kTd−A/V1), whereTdis the drawing temperature,V1the drawing speed, andAa constant. The formation energyEfis 3.8 eV while the precursor concentrationnpis 7×1022g−1. TheE’center concentration at the fiber surface is greater than that at the center because of the transverse difference in the quenching rate during the drawing process. The annealing behavior of theE’center concentration is expressed asnd(t)=nd(0)exp[−&ngr;t exp(−Ed/kTa)], whereTais the annealing temperature. The activation energy for the motion of theE’centersEdis 0.2 eV while the frequency factor &ngr; is 8×10−3sec.−1.

ISSN:0021-8979    

DOI:10.1063/1.336107

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Minority‐carrier diffusion has been investigated in as‐grown CdZnS/CuInSe2solar cells. Capacitance‐voltage (C‐V) and photoconductivity measurements are combined to determine diffusion and interface recombination processes. Diffusion lengths of about 2 &mgr;m and a small interface recombination velocity are determined from biased photoconductivity, biased spectral response, and photoluminescence studies. Photoluminescence studies also indicate that a much lower interface recombination velocity occurs at the CdZnS/CuInSe2interface than that at a bare CuInSe2surface.

ISSN:0021-8979    

DOI:10.1063/1.336108

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We propose a new negative conductance device consisting of a heterojunction bipolar transistor with a quantum well and a symmetric double barrier or a superlattice in the base region. The key difference compared to previously studied structures is that resonant tunneling is achieved by high‐energy minority carrier injection into the quantum state rather than by application of an electric field. Thus this novel geometry maintains the crucial, structural symmetry of the double barrier, allowing unity transmission at all resonance peaks and higher peak‐to‐valley ratios and currents compared to conventional resonant tunneling structures. Both tunneling and ballistic injection in the base are considered. These new functional devices have significant potential for a variety of signal processing and multiple‐valued logic applications and for the study of the physics of transport in superlattices.

ISSN:0021-8979    

DOI:10.1063/1.336109

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Dousmanisetal. [Phys. Rev.133, A316 (1964)] demonstrated that GaAs light‐emitting diodes could produce a cooling effect if the quantum efficiency (ratio of photon flux to junction current) is very close to unity (e.g., >0.97). Here, it is pointed out that for narrow‐bandgap semiconductors, the quantum efficiency need not be so high to produce cooling. Also, for narrow‐bandgap semiconductors there is an additional cooling mode in which the reverse‐biased diode cools its radiant environment by absorbing infrared radiation. Maximum cooling rates per unit of junction area are on the order ofn2&sgr;T4, wherenis the index of refraction, &sgr; is the Stefan–Boltzmann constant, andTis the temperature. For small cooling rates the efficiency for cooling can approach the limit imposed by the second law of thermodynamics.

ISSN:0021-8979    

DOI:10.1063/1.336309

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Radiation sensing field effect transistors display a variety of nonlinear and saturating responses to ionizing radiation. A model involving the numerical solutions to the photoconductivity equations is presented which describes the response under a wide range of radiation doses and applied fields. The large, unexpected, response for zero bias demonstrates the importance of diffusion of the photocarriers. The simulations are consistent with the known transport parameters for SiO2, with the main unknowns being the concentration of electron and hole traps. A variety of data at different applied voltages and doses can be fit with the same transport parameters.

ISSN:0021-8979    

DOI:10.1063/1.336110

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple analytical theory is developed to describe the carrier distribution and the current flow in a punch‐through structure under the diffusion‐limited injection condition and negligible generation recombination effects. The current expression determined is similar to the diode current expression with the diffusion length replaced by the injection length. According to the nature of the injection length, the current flow process is found to be intimately related to the doping concentration and carrier mobility in the base. Recombination generation effects are next included in the theory to account for the photogain observed in punch‐through structures. Finally the model is applied to the gate‐field‐controlled barrier‐injection transit‐time transistor and the field and light injection‐controlled punch‐through transistor.

ISSN:0021-8979    

DOI:10.1063/1.336111

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The thermal exchanges in a quartz crystal resonator are investigated. This leads to a temperature gradient distribution which is in the main plane of the crystal, and therefore does not exhibit any functional dependence (at least at the first order) along the plate thickness. Internal heat source due to the energy dissipation by the internal friction is considered. The corresponding in‐plane thermal stresses are calculated in the isotropic approximation, and anisotropy is introduced by means of the stress‐strain relations. Applying a perturbation method, the resulting frequency shifts are obtained for both static and dynamic thermal behaviors.

ISSN:0021-8979    

DOI:10.1063/1.336112

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper describes a planar photoelectrochemical structure consisting of a thin porous layer ofnonmetallized semiconducting powder above a metallic film. Suited to the photocatalysis of redox reactions in an aqueous gas‐phase environment, the properties of the structure are illustrated using the TiO2sensitized photodecomposition of formic acid which was observed to occur at quantum efficiencies as high as 30%. A photoelectrochemical mechanism is proposed which is the powder‐layer analogue of that describing the catalytic activity of dispersed metallized powders. The approach holds potential for fabricating more complex photochemical structures as well as providing new ways of studying powder‐sensitized reactions.

ISSN:0021-8979    

DOI:10.1063/1.336113

出版商:AIP    

年代:1985

数据来源: AIP