摘要:

The electronic and optical properties of Ge‐doped vapor epitaxial indium phosphide were studied. From Hall‐effect measurements, it was determined that the Ge‐doped material was heavily compensated even for highly doped material. The defects responsible for compensating the InP were investigated by low‐temperature photoluminescence measurements at 10 K. Strong acceptor‐related transitions at 1.379 and 1.395 eV were observed in the doped material. Deep‐level emission at 1.17 eV was also observed in the heavily doped material. The relationship between these bands and compensation is discussed. The observed doping dependence of Ge in InP suggests that self‐compensation by native defects may be important in determining the electronic properties of group IV doped III‐V compounds in support of recent theoretical predictions.

ISSN:0021-8979    

DOI:10.1063/1.346786

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Polymeric thin films were prepared from gaseous titanium tetraisopropoxide by low‐temperature plasma polymerization. The films exhibitedn‐type semiconductor properties and showed conductivities in the range between 10−8–102s/cm. High photocurrent under irradiation of 30 mW/cm2of visible light was observed which exceeded the value found for plasma‐polymerized copper acetylacetonate thin films by nearly three orders of magnitude. From x‐ray photoelectron spectroscopy analysis, it was found that the films largely consist of metallic and organic layers corresponding to TiOx(0<x<2) and (CH2)n, respectively. Transmission electron micrograph observations and electron diffraction measurements made it possible to conclude that the film has a specific texture consisting of amorphous metal layers with an average thickness of 15–25 nm inside a polymer matrix.

ISSN:0021-8979    

DOI:10.1063/1.346787

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The noncontact transient grating technique under constant electron‐hole pumping to the density 4×1019cm−3was used to characterize the ambipolar diffusion coefficientDain Si:Al, Si:In, and Si:Sb molecular‐beam‐epitaxy‐grown layers.Dawas found to be almost constant at a value of ≊8 cm2/s up to an equilibrium carrier density of 2×1019cm−3in the layer and was independent of the doping type. At higher doping density, evidence for a sharp increase inDawas observed. For example,Daincreased to a value of 20 cm2/s at a doping density of about 1020cm−3. TheDabehavior is in reasonable agreement with results of the high‐density ambipolar diffusion theory of Young and van Driel and is incompatible with majority‐carriers diffusion coefficients according to the formulaDa= 2DnDp/(Dn+Dp). An explanation for this behavior is given.

ISSN:0021-8979    

DOI:10.1063/1.346788

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Minority‐electron transport inp‐GaAs with a wide range of acceptor doping concentration from 1017to 1019cm−3is studied in detail. Using the Monte Carlo method in which electron‐hole interactions are taken into account, electron transport properties inp‐GaAs, such as drift velocity and electron temperature, are calculated. The calculated results show good agreement with the experimental ones. Furthermore, in order to make the features of minority‐electron transport clear, the electron transport properties inn‐GaAs, where electrons act as majority carriers, are also calculated. In comparison with majority‐electron transport, drift velocity, and electron temperature for the minority electron are greatly reduced. Throughout the study, it is shown that the interaction with holes is essential for minority‐electron transport inp‐GaAs.

ISSN:0021-8979    

DOI:10.1063/1.346789

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Single crystals of the group IVa to VIII transition‐metal disilicides, namely TiSi2, VSi2, CrSi2, MoSi2, &agr;FeSi2, and CoSi2, have been successfully grown by a floating‐zone method. Temperature and crystallographic dependencies of the resistivity have been measured in the temperature range from 4.2 K to room temperature. The resistivity of all the disilicides show a positive temperature dependence and some anisotropy. The thermal component of the resistivity changes systematically with the group number of the metal elements and correlates well with thedband density of states at the Fermi energy.

ISSN:0021-8979    

DOI:10.1063/1.346790

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Negative‐electron‐affinity GaAs photocathodes have been improved by optimizing the (Cs,O)/GaAs interface. An optimum interface can be obtained by annealing the preoxygenated substrate surface at elevated temperatures (∼450 °C) prior to the (Cs,O) activation. Furthermore, the results of experiments with the aid of x‐ray photoelectron spectroscopy demonstrate that the direct bonding of oxygen to substrate atoms is most likely the origin of the interfacial barrier to electron escape.

ISSN:0021-8979    

DOI:10.1063/1.346791

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical properties of grain boundaries have been investigated by means of capacitance measurements such as deep‐level transient spectroscopy and thermally stimulated capacitance. This paper describes the evolution of the electrical properties ofn‐type &Sgr;=25 silicon bicrystals as a function of heat treatments. It results from this work, that after annealing and quenching, the &Sgr;=25 bicrystal presents an electrical activity and that metallic impurities are responsible for the grain boundary electrostatic potential barrier. The investigations by transmission electron microscopy have shown that the grain boundary activity is in relationship with the presence of colonies of precipitates at the interface, these precipitates being silicides. The results of microanalysis experiments made elsewhere on other similar bicrystals indicate the presence of copper and nickel in the precipitates forming the colonies. The importance of the heating and cooling rates of the samples about the energy distribution of the interface states display the kinetic aspect of the mechanisms involved (segregation‐precipitation).

ISSN:0021-8979    

DOI:10.1063/1.346792

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thermal stability for Pd/n‐GaSb Schottky contacts is analyzed and studied. At room temperature, Pd/n‐GaSb Schottky diodes have better performance, but when the annealing temperature is increased to 300 and 450 °C for 30 min, Schottky contacts gradually become ohmic contacts. From the measurement of Rutherford backscattering spectroscopy and x‐ray diffraction analysis, the result indicates that the interdiffusion between palladium and gallium forming Ga5Pd is the dominant factor for degrading properties of Schottky diodes.

ISSN:0021-8979    

DOI:10.1063/1.346793

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electromechanical performance limits of a tube scanner type, scanning tunneling microscope are analyzed with respect to the three figures of merit: noise level, scan speed, and scan range. A simple tradeoff between the tube resonant frequency and scan range is defined. For a critically damped scanner tube, a good balance between scan speed and scan range is achieved with a preamplifier bandwidth equal to the resonant frequency of the scanner tube, in which case the closed loop control system bandwidth (90° phase margin) is 2/&pgr; times the resonant frequency of the tube, for a proportional‐integral controller. This control loop bandwidth is shown to be compatible with a noise performance that is limited by shot noise in the tunnel junction.

ISSN:0021-8979    

DOI:10.1063/1.346794

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A four‐terminal Hall resistance is analyzed using the Bu¨ttiker formalism of contacts. The possible maximum deviation of a quantized Hall resistance from ideal values in a multiterminal device is shown to be limited by the resistances of contacts. A general expression for the possible maximum deviation is derived for a multiterminal configuration with an arbitrary number of terminals in the condition of an arbitrary (integer) number of filled Landau levels. The influence of an inhomogeneous two‐dimensional electron gas on the Hall resistance is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.346795

出版商:AIP    

年代:1990

数据来源: AIP