摘要:

A comparative study of the interfacial reactions between Pd anda‐Ge:H, deposited atTS=150 °C (low temperature, LT) and atTS=200, 300 °C (high temperature, HT), was carried out by x‐ray diffraction and Auger electron spectroscopy after sample annealing in the regime ofT=200–300 °C andt=1/4–4 h. It was found that the Pd/a‐Ge:H(LT) formed a much more stable Pd2Ge interfacial layer, compared to the Pd/a‐Ge:H(HT) system in which the Pd2Ge was transformed to PdGe. The main difference between the LT‐ and the HT‐a‐Ge:H films is probably the structure of the material. Whereas the HT films are compact, the LT‐a‐Ge films contain a network of voids which slow down the diffusion of Ge to the interface.

ISSN:0021-8979    

DOI:10.1063/1.353449

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Due to the fact that impurities normally change their doping characters when they undergo shallow to deep transitions or deep‐to‐false‐valence transitions, a single defect, such as a cation on an Sb site, can explain all of the following facts for nonintentionally doped AlxGa1−xSb alloys and InAs/AlxGa1−xSb superlattices and quantum‐well structures: (i) Bulk GaSb isptype; (ii) bulk AlSb is semi‐insulating; (iii) InAs/AlSb superlattices with InAs quantum wells thicker than a critical thicknessdc(x=1.0) arentype, where the InAs shallow–deep critical thickness functiondc(x) is around &bartil;100–&bartil;150 A˚ for 0.5<x≤1.0 for InAs/AlxGa1−xSb superlattices; (iv) InAs/AlSb superlattices with InAs quantum wells thinner thandc(x=1.0) are semi‐insulating. In addition, the theory predicts that Al0.5Ga0.5Sb and AlSb will be semi‐insulating when nonintentionally doped, but can be converted toptype by the application of hydrostatic pressureP:P≳90 kbar andP≳150 kbar, respectively. These changes of doping character, which lie outside the conventional effective‐mass theory, occur often in type‐II band‐alignment systems, such as InAs/AlxGa1−xSb.  

ISSN:0021-8979    

DOI:10.1063/1.353450

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The effect of nonpolar optical phonon scattering on the free‐carrier absorption inn‐type semiconductors such as germanium has been investigated quantum mechanically in quantizing magnetic fields. It is assumed that the energy band structure of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for conduction electrons is of the nonpolar optical phonon scattering. When the radiation is polarized parallel to a dc magnetic fieldB, the absorption coefficient appears to be of a complex value due to the interaction between the radiation field and the optical phonon field in nondegenerate semiconductors. Results show that the real part of the absorption coefficient oscillates with the magnetic field in the high‐field region, and imaginary part of the absorption coefficient appears with a few extremum points (peaks and dips) in high magnetic fields. These are different from those of the acoustic phonon scattering in III–V compound semiconductors such as InSb or GaAs, in which the absorption coefficient oscillates with the magnetic field in lower magnetic fields and then increases monotonically with the field.  

ISSN:0021-8979    

DOI:10.1063/1.353423

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A simple, practical method is described to extract the carrier concentration and mobility of each component of a multicarrier semiconductor system (which may be either a homogeneous or multilayered structure) from variable magnetic field measurements. Advantages of the present method are mainly due to the inclusion of both the longitudinal and transverse components of the conductivity tensor and normalization of these quantities with respect to the zero‐field longitudinal component of the conductivity tensor. This method also provides a simple, direct criterion by which one can easily determine whether the material under test is associated with a one‐carrier or multicarrier conduction. The method is demonstrated for a simple one‐carrier system [GaAs single‐channel high‐electron‐mobility‐transistor (HEMT) structure] and two multicarrier systems (an InGaAs‐GaAs double‐channel HEMT structure and two types of carriers present in an InGaAs single‐channel HEMT structure). The analysis of the experimental data obtained on these samples demonstrates the utility of the method presented here for extracting carrier concentrations and mobilities in advanced semiconductor structures.

ISSN:0021-8979    

DOI:10.1063/1.353424

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Effects of residual metal impurities after RCA (Radio Corporation of America) standard cleaning (alkaline and acid rinses) on the generation of ac surface photovoltages (SPVs) are investigated usingn‐type silicon wafers. Aluminum (Al) and iron (Fe) in the native oxide induce a negative charge, causing high ac SPVs inn‐type wafers. The ac SPV dependency on the concentration of Al and Fe is determined. Nickel and zinc, however, have little effect on the generation of ac SPVs. In commonly employed cleaning processes, Al is the major impurity in the native oxide, and thus the ac SPV technique is applicable to nondestructive diagnostics for quality control in cleaning processes.

ISSN:0021-8979    

DOI:10.1063/1.353425

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The behavior of semi‐insulating InP:Fe under high electric field is investigated. The current‐voltage (I‐V) characteristics are studied on both long liquid‐encapsulated Czochralski‐grown samples and short epitaxial‐grown layers. These characteristics show a linear regime at low voltages followed, for higher voltages, by a nonlinear behavior and a current breakdown. The critical electric field at which the nonlinearity begins is found to be independent of the sample thickness, the material compensation, and the nature of the contacts, and is equal to 10 kV/cm. This fact rules out the usual explanation in terms of Lampert’s injection theory. In the nonlinear regime, a slow transient response (≊1 s at room temperature) is observed only for long samples. The time constant of this effect exhibits a thermal activation energy (≊0.64 eV) close to that of the iron‐related deep level. Field‐dependent effects on the thermal emission rate and the capture cross section are discussed. Considering a field enhancement of the capture cross section, we propose a model to explain both the nonlinear characteristics and the slow dynamic behavior of long samples. The current breakdown observed at higher fields is attributed to an impact ionization of the deep levels and not to a trap‐filled‐limit voltage as previously reported.

ISSN:0021-8979    

DOI:10.1063/1.353426

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Undoped GaSb epilayers were grown on GaSb and GaAs substrates using the metalorganic chemical vapor deposition (MOCVD) technique, and photoluminescence (PL). Hall effect measurements were used to characterize the undoped epilayers. For undoped GaSb epilayers, four energy levels revealed by PL spectra are shown to be due to acceptors, usingKTdp/dEfvaEf‐Evdata obtained from Hall effect results, wherepis the hole concentration,EfandEvare the Fermi level and the top of valence band, respectively. The acceptor levels lie at 3, 58, 80, and 130 meV above the top of valence band, respectively. The donor level is 15 meV below the bottom of the conduction band. These acceptor levels exist in almost all of the undopedp‐type GaSb epilayers grown at high temperature, while the donor level exists only in the undopedn‐type GaSb epilayers grown by low‐temperature MOCVD. It is found that these levels may be changed using the different growth temperatures.

ISSN:0021-8979    

DOI:10.1063/1.353427

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The off‐state leakage characteristics ofn‐channel metal‐oxide‐semiconductor field‐effect transistors with pure oxide, low‐partial pressure nitrided (LPN) oxide, re‐oxidized LPN, and nitrogen‐annealed LPN oxide as the gate insulator, were investigated over the temperature range 300–400 K. In the high‐field region (above 7 MV/cm), the gate‐induced drain leakage was found to be due to band‐to‐band tunneling for all samples. Low‐field conduction was determined to be due to a gate current which was many orders of magnitude higher than the Fowler–Nordheim current observed in capacitors on the same wafers. A trap‐assisted tunneling model was employed, using a trap energy of 0.7 eV determined from the activation data, in order to explain the low‐field gate current. The most likely cause of this enhanced conduction is oxide degradation in the gate‐to‐drain overlap region created during the source/drain implant.

ISSN:0021-8979    

DOI:10.1063/1.354086

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Electrical transport properties of phosphorus‐dopedp‐type CdTe single crystals and phosphorus‐ion‐beam doped, homoepitaxial thin films have been investigated by means of van der Pauw Hall effect and resistivity measurements as a function of temperature from 8 to 400 K. Analysis of the data indicates a maximum doping level greater than 2×1017cm−3in the films, at least as high as in the single crystals. Phosphorus has an ionization energy of about 40 meV, the degree of compensation is smaller in the films, room temperature mobilities of the films are lower than those for single crystals by about 20%, and the temperature dependence of mobility is similar for both crystals and films. Impurity scattering is dominant at lower temperatures and polar mode scattering is dominant at higher temperatures with a maximum mobility at 150–190 K. Both the single crystals and the ion‐assisted doped films show a temperature independent resistivity at temperatures below 40 K, indicating the presence of impurity band conduction.

ISSN:0021-8979    

DOI:10.1063/1.353428

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A procedure for the fabrication of two‐dimensional carrier (electron and hole) gases in modulation doped GeSi/Si heterostructures is presented. The best 4.2 K mobilities measured for the two‐dimensional electron and hole gases are 180 000 cm2/V s and 18 000 cm2/V s, respectively. Recently, two‐dimensional hole gases with mobilities as high as 55 000 cm2/V s have been obtained. The carrier gases are fabricated on top of relaxed, compositionally graded GexSi1−xbuffer layers with low threading dislocation densities (≊106cm−2). Experimental evidence indicates that the function of the graded buffer is to promote dislocation propagation while suppressing nucleation. A comparative analysis is carried out for two dimensional electron gases in GeSi/Si/GeSi and in AlGaAs/GaAs structures. Although molecular beam epitaxy is used to grow the samples, the principle discussed here is independent of growth technique.

ISSN:0021-8979    

DOI:10.1063/1.353429

出版商:AIP    

年代:1993

数据来源: AIP