摘要:

We calculated a more accurate density of states (DOS) profile from field‐effect (FE) measurements in hydrogenated amorphous silicon thin‐film transistors, taking into account the anomalously changing conductivity prefactor in accordance with the Meyer–Neldel (MN) rule. We present a self‐consistent analysis of the density of gap states profile, where the MN rule is, for the first time, properly considered in relation to the nonuniform shift of the Fermi level as induced by the field effect. Moreover, the calculation yields the correct flat‐band voltage and the corresponding flat‐band activation energy. The determination of conductivity activation energies free from any initial band bending effects is of importance in all types of transport measurements.

ISSN:0021-8979    

DOI:10.1063/1.337407

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Decreasing device dimensions will cause an increasing internal field strength in a semiconductor device. The average carrier energy is different from the thermal equilibrium value 3/2kT. Modification of current transport is considered on different levels of approximation. In a local approximation wederivea field‐dependent carrier mobility and temperature from a more general self‐consistent formulation. Numerical estimation of hot‐electron effects are given for a realisticn‐channel metal‐oxide‐semiconductor field‐effect transistor of various channel lengths. It is shown that both high‐field and field‐gradient effects will contribute.

ISSN:0021-8979    

DOI:10.1063/1.337408

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper reports a study of the electrical properties of a systematic series of InP/In0.53Ga0.47As modulation‐doped heterostructures grown by metalorganic chemical vapor deposition. Both Hall‐effect and Shubnikov–de Haas measurements are used to obtain consistent values for carrier densities and mobilities. The heterostructures are shown to display a persistent photoconductive effect at low temperatures (<80 K) which results in changes in both the carrier density and the mobility. The variation of mobility with carrier density is analyzed to show that alloy disorder and background charged impurity scattering are the dominant scattering mechanisms. Excitation across the InP band gap is shown to be necessary for the persistent photoconductivity. We propose a mechanism for this effect in which electron hole pairs created by illumination are separated by electric fields built into the heterojunction with the holes subsequently being trapped in the InP substrate.

ISSN:0021-8979    

DOI:10.1063/1.337409

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have measured sheet resistance and mobility changes for a series of In0.53Ga0.47As layers as a result of hydrogen, boron, and beryllium implantation. We find that boron and beryllium implantation can produce a two order‐of‐magnitude increase in sheet resistance due mainly to a decrease in mobility accompanied by a smaller decrease in the sheet carrier concentration. Hydrogen implantation results in a decrease in sheet resistance due to an increase in electron concentration accompanied by only a small mobility decrease. The increase in sheet resistance due to boron and beryllium implants is not large enough to have obvious application for device isolation.

ISSN:0021-8979    

DOI:10.1063/1.337410

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Current transient measurements are carried out on ion‐implanted polymers to provide new information on the mechanism for the implantation‐induced conductivity. Using metal‐oxide‐semiconductor field‐effect transistor devices in which implanted polymer films form part of the metal‐oxide‐semiconductor structure, the dispersion parameter &agr; is measured as a function of ion fluence and temperature. The fluence dependent measurements provide evidence for trapping sites and support a trap‐controlled hopping mechanism for ion‐implanted polymers. The temperature‐dependence measurements favor conduction by hopping between traps in the defect band in the mobility gap rather than between traps in the mobility edges. New results are also presented on the dc conductivity of polymers implanted at low temperature (77 K), the same samples as were used for the current transient measurements.

ISSN:0021-8979    

DOI:10.1063/1.337411

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We calculated the shift of Fermi energyEFwith temperature, using a model density of states for hydrogenated amorphous silicon (a‐Si:H) similar to that of deep level transient spectroscopy results, by a numerical method. The conductivity &sgr; was calculated from the calculatedEFas a function of temperature. It was found that some features of anomalous transport phenomena ofn‐typea‐Si:H such as kinks or the continuous bending of log &sgr; vs 1/Tcurves and the Meyer–Neldel‐type preexponential factors can be explained, at least in part, by the statistical shift alone.

ISSN:0021-8979    

DOI:10.1063/1.337412

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Both secondary ion mass spectrometry and transmission electron microscopy have been used to characterize Au–Ni–Ge and Au–Ag–Ge ohmic contacts to modulation‐doped GaAs/AlGaAs heterostructures. The time periods for alloying the contact were kept to a minimum (<25 s) in order to obtain controlled diffusion of Ge into the semiconductor. Structural analysis shows that a stable alloy contact is formed after 3 s of alloying at temperatures above the Au–Ge melting point. There were no major structural or compositional changes observed with longer alloying times. The Ge‐rich region has a tendency to regrow epitaxially on the GaAs after alloying, as shown by high‐resolution electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.337413

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A space‐charge mapping technique was used to measure the space charge and internal electric fields in metal–poly(ethylene terephthalate)–metal samples subjected to electric field stressing. From these results the role of electronic injection and transport in the observed electrical properties of capacitor structures could be inferred. Below breakdown fields, there was no evidence that the dark current can be attributed to electronic processes. As breakdown fields were approached, a decrease in the injected space charge trapped adjacent to the electrode was observed. This behavior was attributed to the onset of tunneling into high‐energy electronic states in the polymer. This process may produce large current densities leading to dielectric breakdown.

ISSN:0021-8979    

DOI:10.1063/1.337414

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have developed a technique for the fabrication of shallow, silicided junctions with good electrical characteristics. By the implantation of suitable impurity ions into titanium silicide layers on Si formed by ion‐beam mixing and low‐temperature annealing, and the subsequent diffusion of the implanted ions at high temperature into the Si substrate, shallowp+/n,n+/p, and double‐diffusedn+‐n−/pjunctions with silicide ohmic contacts have been obtained. Results of contact resistance, contact morphology, junction integrity, and carrier concentration profile are reported. The effects of implantation energy, implant dose, and annealing parameters are discussed. This technique can be easily applied to the fabrication of metal‐oxide‐semiconductor field‐effect transistors in a self‐aligned fashion.

ISSN:0021-8979    

DOI:10.1063/1.337415

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report field‐effect measurements of the density‐of‐states (DOS) distribution in the last‐deposited surface of undoped glow‐dischargea‐(Si,Ge):H alloy films containing up to 15% Ge. Over the energy range investigated (Ef≤E≤Ef+0.4 eV) the DOS exhibits a peak approximately 0.7 eV belowEc, and the total number of midgap states increases monotonically by a factor of 2 with Ge content. No structure specifically attributable to Ge defect states is seen. These results are interpreted in terms of a diphasic microstructural model of the alloy films.

ISSN:0021-8979    

DOI:10.1063/1.337416

出版商:AIP    

年代:1986

数据来源: AIP