摘要:

In contrast with recent suggestions we show that frequency dependent capacitance‐voltage (C‐V) characteristics can yield information on the state distribution in the forbidden gap of semiconductors which have a continuous state distribution there. For this purpose we have applied an analysis which is based on the solution of the Poisson equation in various sections of the space‐charge region. Then, by using a new recursion approach we found new general expressions for the frequency and temperature dependence of theC‐Vcharacteristics. The present work yields analytic results and a transparent physical picture so that clear correlation is obtained between features of the above characteristics and features of the state distribution. In particular, it is shown that under deep depletion the well‐known linear 1/C2vsVrelation is maintained regardless of the state distribution. This enables the use of the frequency, or temperature, dependence of the corresponding slope for the evaluation of the state distribution from experimental data.

ISSN:0021-8979    

DOI:10.1063/1.335890

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper we present an experimental method for the derivation of the state distribution in the pseudogap of an amorphous material. The method is based on capacitance‐voltage (C‐V) measurements and on transient capacitance interpretation. Analysis of the frequency and temperature dependence of theC‐Vcharacteristics, obtained under deep depletion conditions, enables a differential determination of the density of states in part of the forbidden gap. This approach is shown to have advantages over other capacitance‐based methods in particular for routine comparative studies. In the present work we have measured phosphorus‐dopeda‐Si:H (hydrogenated amorphous silicon) materials which have been prepared under similar conditions in three different laboratories. The results indicate that the discrepancy found in the density‐of‐states maps derived in different laboratories are due more to the different data interpretations than to real variations between the materials. The map derived here is found to be in general agreement with results obtained by other transient capacitance methods. In particular, the presence of a wide peak in the density of states, the center of which is around midgap. The peak increases with increasing dopant concentration but the rise in the Fermi level and the doping efficiency appear to be associated with the fine details of the density‐of‐states dip which lies between the above peak and the sharply rising conduction band tail.

ISSN:0021-8979    

DOI:10.1063/1.335891

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Configurationally bistable defects can exist in either of two different structural configurations for the same charge state. Each configuration exhibits distinct optical and electronic properties. Here a framework is presented for the use and interpretation of deep level capacitance transient spectroscopy measurements in the study of these defects. Examples are presented for the MFe center in InP, a bistable A‐center‐related defect in Si, and the EL2 center in GaAs.

ISSN:0021-8979    

DOI:10.1063/1.335892

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Analytical formulas for evaluating Fermi–Dirac integral of order (1)/(2) has been proposed. The formulas exhibit a degeneracy factorCwhich controls essentially the applicability of the integrals both to the nondegenerate as well as highly degenerate semiconductors. The accuracies with which the derivative can be evaluated by differentiation and integration of the proposed formulas are acceptable. The formulas have been successfully used in the calculation of effective carrier concentration and current density.

ISSN:0021-8979    

DOI:10.1063/1.335893

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Indium oxide/indium phosphide heterojunction solar cells have been fabricated in which the transparent conductiven‐type indium oxide films were deposited in two steps by reactive evaporation of indium on thep‐type InP single‐crystal substrates. The cells were heat resisting up to 500 °C in air and had a solar power conversion efficiency of 16.3% without antireflection coatings.

ISSN:0021-8979    

DOI:10.1063/1.335894

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Room‐temperature Hall mobility as a function of pressure (0–8 kbar) has been measured for high‐purity liquid‐phase‐epitaxy‐grown Ga1−xAlxAs layers. GaAs‐like band structure of low‐composition alloys has also been converted to Si‐like band structure at high pressures and the Hall mobility measured as a function of temperature (77≲T≲300 °K) with crystals locked under constant pressures. The data have been analyzed to identify and distinguish the presence of space charge and alloy scatterings both characterized by mobilities limited byT−1/2. The space charge scattering has been found to be absent in all the crystals studied exceptx=0.047. The alloy scattering potential for electrons in the &Ggr; minimum has been shown to depend on the alloy composition with a maximum value of 1.56 eV atx=0.19. For electrons in theXminima, this potential has been found to be independent of composition with a value of only 0.4 eV.

ISSN:0021-8979    

DOI:10.1063/1.335895

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Complex conductivity measurements of unannealed and annealed semi‐insulating GaAs crystals are reported. A model of fluctuations of well‐defined magnitude superimposed to a Gaussian distribution accounts for the &sgr;ac ∝ &ohgr;2dependence observed above 106Hz in some unannealed samples. The effect of annealing on the magnitude of long‐range potential fluctuations and on the average carrier density is analyzed.

ISSN:0021-8979    

DOI:10.1063/1.335896

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It can generally be considered that an actual contact makes an angle with the extension of the contact surface because the tip of a contact element is convex in shape (macroscopically) and has surface roughness (microscopically). The effect of this angle on constriction resistance and contact resistance for a point contact is analyzed theoretically by solving Laplace’s equation subject to boundary conditions determined by a modeled morphology of the contact. The analysis leads to the modified formulas for the constriction resistance and the contact resistance, which show that the effect cannot always be neglected and that the contact model with space angle is useful.

ISSN:0021-8979    

DOI:10.1063/1.335897

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Various Si and Ge rectifier diodes are tested at frequent intervals of &ggr;‐radiation doses for changes in ideality factor &eegr; and minority carrier lifetime &tgr;. Although both parameters are well known to decrease with dosage, here they are probably for the first time measured to also subsequently increase, decrease, increase, etc., at higher dosages. Examination of diodes in vacuum prior to and following even modest irradiation levels indicates experimentally that noticeable changes in surface properties have been induced by the irradiation. Such experimental techniques permit greater insight into the basic structure of surface phenomena long suspected to play a significant role in diode changes brought about by nuclear irradiation. Utilization of such surface changes leads to a broad general concept to explain the reversals and changes in the dosage dependences of &eegr; and &tgr; in terms of bulk versus surface effects.

ISSN:0021-8979    

DOI:10.1063/1.335898

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Graded heterojunction InGaAs ohmic contacts to GaAs have been prepared which show improved electrical and mechanical properties. The improvements result from the use of a thin Pt layer between the In layer and the substrate which controls the reaction of the In and the GaAs. Evidence is also offered that the InAs heterojunction regions are epitaxial.

ISSN:0021-8979    

DOI:10.1063/1.335899

出版商:AIP    

年代:1985

数据来源: AIP