摘要:

The electron and hole traps occurring in melt‐grown undopedn‐type GaAs have been studied using deep level transient spectroscopy. Several electron traps with energies ranging from 0.81 to 0.14 eV below the conduction band, as well as three hole traps having energies 0.65, 0.56, and 0.43 eV above the valence band, were measured. Isochronal annealing in the temperature range 500–800 °C indicated that, under optimized ‘‘face‐to‐face’’ annealing conditions, an 800 °C heat treatment for 1 h resulted in the removal of all the electron traps, with the exception of the EL2 (0.81 eV). Near the surface, however, this annealing procedure reduced the EL2 concentration by more than an order of magnitude. It was further observed that, when a sample is annealed ‘‘face‐to‐face’’ with another sample, the total defect concentration is reduced much more than when a sample is covered with graphite as during a standard liquid‐phase epitaxy (LPE) pregrowth anneal cycle at the same temperature. The effect of surface damage during mechanochemical polishing on defect concentration has also been demonstrated.

ISSN:0021-8979    

DOI:10.1063/1.336854

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Zn‐doped GaAs diffused with Sn has been examined in cross section by transmission electron microscopy (TEM) and high‐resolution cathodoluminescence (CL) in an attempt to account for the penetration of Sn into this material but the apparent lack of any electricity activity. TEM shows that small Sn‐rich precipitates are present in the GaAs near the surface. CL indicates that some of the Sn dopes of GaAsn‐type, but additionally that new emissions in the spectra at ∼1.44 and ∼1.455 eV are seen to originate from the diffused region. A possible explanation for the lack of electrical activity of the Sn is discussed in terms of these results and may lie in the formation of a compensating Sn‐related complex or an accumulation of Zn in the diffused region.

ISSN:0021-8979    

DOI:10.1063/1.336855

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An examination of majority‐carrier deep level transient spectroscopy (DLTS) spectra for GaAs with filling pulse heights in the vicinity of the flat‐band voltage has revealed a subtle anomalous peak with the ‘‘correct’’ sign: one that would normally be associated with emission from a majority‐carrier trap. A model is presented which explains the peak as one of a class of peaks due to minority‐carrier capture into a minority‐carrier trap. Good agreement is found between the experimental and calculated trap signatures (T2&tgr; vs 1/T) assuming the minority‐carrier trap to be Fe (a residual impurity which is observed in optical DLTS spectra on the same sample). The importance of using optical DLTS data to assist in properly interpreting the majority‐carrier DLTS spectra is stressed.

ISSN:0021-8979    

DOI:10.1063/1.336856

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Electron emission rates and capture cross sections at the gold acceptor level have been obtained in siliconp+/ndiodes with phosphorus concentrations of 1.2×1012cm−3and 5×1014cm−3, showing no phosphorus concentration dependencies. This indicates negligible electric field dependence of the electron emission rate in the range 102–105V/cm and supports the contention that the capture cross section is independent of the phosphorus dopant impurity concentration. The magnitude of the capture cross‐section data supports a neutral potential model of the gold acceptor center.

ISSN:0021-8979    

DOI:10.1063/1.336857

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Solid solutions of CoSi2and NiSi2were prepared from the solid‐state reaction of thin films of Ni‐Co alloys with their silicon substrates. The room‐temperature resistivity of these silicide solid solutions does not increase parabolically, but (within the sensitivity of the measurements) varies linearly with composition. A model is proposed which explains the very weak alloy scattering on the basis that in these disilicides (a) thedbands are pushed below the Fermi level, (b) conduction occurs mostly viaselectrons, and (c) there is nos‐dscattering.

ISSN:0021-8979    

DOI:10.1063/1.336858

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The photocapacitance of a thin‐film CdZnS/CuInSe2heterojunction was observed under white light excitation. Capacitance increases were observed that were indicative of minority‐carrier trapping in the junction. Emission spectroscopy indicated that a distribution of traps produce this signal. Analysis of the data indicate trap distributions ranging from 5×1014cm−3to 1.6×1015cm−3in the bulk and 3.3×1011cm−2at the surface. Photovoltaic efficiency was inversely related to the photocapacitance signal. A model relates deep electron interface states to a decrease in open‐circuit voltage.

ISSN:0021-8979    

DOI:10.1063/1.336859

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We examine the effective resistivity of inhomogeneous materials, in particular two‐phase materials, which are statistically homogeneous and isotropic. A review of methods used to determine the effective resistivity is given. Comparisons are made between the traditional methods for continuous materials and resistor network calculations. The purpose is to clarify to what extent it is possible to describe a continuous, inhomogeneous material, with significantly differing constituent resitivities by discrete resistor models. Four discretization procedures, the aim of which are to determine the effective resistivity of such materials, are proposed and discussed. The applicability of discretization procedures is tested against a specific example, the checkerboard. It is shown that none of the discretization models may be expected to give a good description of the material. This fact is intimately related to the difference in duality properties of continuous and discrete systems.

ISSN:0021-8979    

DOI:10.1063/1.336860

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have studied the pressure dependence of the tunneling resistance of tunnel junctions between 300‐nm‐thick Bi films and 20‐nm‐thick films of Al deposited at room temperature. Native Al oxide formed by oxygen glow discharge provided the tunnel barrier. The resistance was measured as a function of voltage from 0 to about 1 V. Measurements were made from room temperature to below the superconducting transition temperature of the Al film. The pressure range covered was from 0 to about 8 kbar. The resistance decreases with increasing pressure in a way easily described by simple tunneling theory. In the resistance curves we observe pressure dependence of structure, which has in the past been associated with the pressure dependence of the Bi band structure.

ISSN:0021-8979    

DOI:10.1063/1.336861

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new iterative method for solving the discretized nonlinear Poisson equation of semiconductor device theory is presented. This method has two main advantages. First, it converges for any initial guess (global convergence). Secondly, the values of electric potential are updated at each mesh point by means of explicit formulas (that is, without the solution of simultaneous equations). The first property makes this method quite robust, while the second allows for the implementation of the method on computers with small RAMs. Some numerical results obtained by this method are reported.

ISSN:0021-8979    

DOI:10.1063/1.336862

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The band alignment in GaAs:(Al,Ga)As heterostructures has been investigated over the full range of alloy composition. The valence‐band discontinuity &Dgr;Evis determined by measuring the activation energy for thermionic emission of holes fromp‐GaAs over an undoped, square (Al,Ga)As barrier. The use ofp‐type structures to measure &Dgr;Evcircumvents a number of complications involved in the measurement of &Dgr;Ec. The parameters required for analysis are determined by different measurements on the same structures and the analysis is performed so that the activation energy, extrapolated to zero bias, yields &Dgr;Evdirectly. It is found that &Dgr;Evis a linear function of the aluminum mole fractionxAl@B:&Dgr;Ev&bartil;0.55xAl(eV) (0≤xAl≤1). The validity of these data is supported by measurements of &Dgr;Ecin the direct band‐gap regime, where complementary values of &Dgr;Evand &Dgr;Ecadd up to the expected band‐gap difference. This relationship provides a simple description of the full band alignment in this heterosystem and should prove valuable as a test of the various heterojunction lineup theories. Moreover, these measurements have a number of important consequences, particularly from the viewpoint of heterojunction devices.

ISSN:0021-8979    

DOI:10.1063/1.336864

出版商:AIP    

年代:1986

数据来源: AIP