摘要:

We report time‐resolved luminescence data on the 155‐eV band of Ge‐doped AlxGa1−xAs withx=0.3, grown by liquid‐phase epitaxy. They are interpreted in terms of donor‐acceptor pair recombinations in which the donors and acceptors have a well‐defined spatial separation. From the analysis of the emission line shape, the optical parameters of the pair are deduced.

ISSN:0021-8979    

DOI:10.1063/1.345338

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The advantages of using multi‐quantum‐well or superlattice systems as the absorbers in concentrator solar cells are discussed. By adjusting the quantum‐well width, an effective band‐gap variation that covers the high‐efficiency region of the solar spectrum can be obtained. Higher efficiencies should result from the ability to optimize separately current and voltage generating factors. Suitable structures to ensure good carrier separation and collection and to obtain higher open‐circuit voltages are presented using the (AlGa)As/GaAs/(InGa)As system. Efficiencies above existing single‐band‐gap limits should be achievable, with upper limits in excess of 40%.

ISSN:0021-8979    

DOI:10.1063/1.345339

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Dark current‐voltage (J‐V) characteristics ofp‐i‐na‐Si solar cells are studied to clarify the effect of thep/iinterface layer on the open‐circuit voltage (Voc). It is shown that the recombination current in thep/iinterface region is predominant in thea‐Si solar cells with ani‐layer thickness of less than 200 nm and has a great effect on the dark‐current transport in the solar cells. It is also shown that the current transport of the cells with thep/iinterface layer of constant band gap of a thickness of more than 14 nm is effectively the same as that of a cell in which the band gap of the wholeilayer is equal to that of the interface layer. A model in which the dark current of the cell consists of the recombination current at thep/iinterface and the recombination current in the bulk region of theilayer is proposed. Using this model, theVocdegradation for thea‐Si solar cells with thep/iinterface layer is shown to be due to the defects generated in theilayer.

ISSN:0021-8979    

DOI:10.1063/1.345340

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A measurement method has been developed which makes it possible to determine the thermal emission rates, the concentrations, and position of the thermal emission region for charge‐carrier emission centers in nonabruptp‐njunctions. A computerized deep‐level transient spectroscopy (DLTS) technique for current transients is used in combination with capacitance measurements. Numerical, iterative calculations of the shallow doping profile of thep‐njunction and capacitance change connected with thermal emission of charge carriers from the emission centers are compared with measured data. Generalized expressions for the determination of carrier emission data from thermal current and capacitance transients are derived for nonabruptp‐njunctions. The method is applicable when the properties of thep‐njunction cannot be chosen arbitrarily, for example, for the study of deep impurity centers in standard types of semiconductor devices where conventional DLTS methods fail.

ISSN:0021-8979    

DOI:10.1063/1.345341

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A model is developed to describe the evolution of a solid armature to the point where metallic contact with the rails is lost. The idea is that a current/melt wave begins at the rear of the armature, where current is concentrated by velocity skin effect, and propagates forward along the rail/armature interface as molten armature material is lost. When the melt wave reaches the front of the armature, the transition to plasma brush contact occurs. A calculation with the model simulating an earlier solid armature experiment at General Atomics shows close agreement with the measured transition velocity, as inferred from the increase in muzzle voltage observed during the shot.

ISSN:0021-8979    

DOI:10.1063/1.345342

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An electrical to optical efficiency of 5% has been demonstrated in an x‐ray preionized XeCl discharge laser using an improved prepulse‐mainpulse circuit, based on resonant charging of the peaking capacitor. In contrast to known prepulse‐mainpulse circuits, the new scheme has no time delay between prepulse and mainpulse nor a voltage reversal on the electrodes. We present three possible configurations of the scheme and one of them has been realized for demonstrating its high‐efficiency capabilities.

ISSN:0021-8979    

DOI:10.1063/1.345343

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The nonlinear physical systems which are described by infinite dimensional integrable equations have two types of solutions: solitons which can be viewed as nonlinear localized ‘‘normal modes’’ and radiation solution which can be viewed as linear modes (termed as phonons, photons, spin waves, etc., in condensed matter physical systems). These linear modes are modulationally unstable to nonlinear normal modes and this instability is expressed by a time domain decay of their amplitude ast−1/2, which corresponds to 1/fspectrum. This mechanism is explored for three types of nonlinear equations and an analogy with 1/fnoise generated as a result of low‐frequency bremsstrahlung is revealed.

ISSN:0021-8979    

DOI:10.1063/1.345344

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effect of relative humidity (0%, 40%, 51%, and 78%) on the stability of YBa2Cu3O7−xwas investigated over a six‐month period using x‐ray diffraction, scanning electron microscopy, and magnetic susceptibility measurements. At 78% humidity, the fraction of superconductive phase decreased parabolically with time. After six months, the powders completely decomposed into BaCO3, Y2BaCuO5, and CuO. Most of the samples placed at humidity levels of 51% or less were in the orthorhombic YBa2Cu3O7−xphase at the end of six months and remained superconducting and stable. However, all powders kept at nonzero humidity levels were heavily agglomerated; some became hard solids with diameters equal to or greater than 0.1 mm. The microstructure of the powder indicated a surface reaction with water undetected by x‐ray diffraction or magnetic susceptibility measurements.

ISSN:0021-8979    

DOI:10.1063/1.345345

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Shallow silicidedn+pjunctions have been formed by implanting arsenic ions into Pt or PtSi films followed by low‐temperature furnace annealing in the N2ambient. Shallow junction diodes with a junction depth of about 0.1 &mgr;m, a forward ideality factor lower than 1.02, and a reverse leakage current density less than 5 nA/cm2at −5 V was achieved with 750 °C, 90‐min annealing. Annealing at higher temperatures results in junction degradation due to Pt diffusion from PtSi into the Si substrate. This may be significantly improved by F+implantation following the As+implantation. The shallow junction processed with the As+/F+dual implantation and a subsequent anneal at 800 °C shows even slightly better characteristics than those annealed at 750 °C without F+implantation.

ISSN:0021-8979    

DOI:10.1063/1.345346

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is experimentally shown for the first time that far field lobe broadening, which is a multilateral mode operation under continuous wave operation in phased array lasers that emit diffraction limit beams under pulsed conditions mainly originates from temperature distribution along the junction plane. Spectrally resolved near field measurements show that pulse width, where broadening occurs, corresponds well to the one where temperature influence appears. Moreover, measurement of temperature distribution by the near field measurements and laser Raman spectroscopy show that a considerable temperature difference does exist between the center and edge elements in the array.

ISSN:0021-8979    

DOI:10.1063/1.345347

出版商:AIP    

年代:1990

数据来源: AIP