摘要:

It is well known that recombination lifetimes are significantly degraded in oxygen‐precipitated silicon. The possible sources for lifetime degradation are expected to be oxygen precipitates (OP’s), dislocation loops, stacking faults, and point defects associated with self‐interstitials generated during the oxygen precipitation process. From the results of an extensive experimental study using IR absorption, TEM, DLTS, and SPV (surface photovoltage), we have found that OP’s are mainly responsible for the observed lifetime degradation and that recombination at OP’s takes place through Si/OP interface states. In addition we have observed that the lifetime degradation is more severe inp‐Si than inn‐Si even for identical densities and sizes of OP’s. A model for recombination at OP’s is presented in terms of the surface recombination velocity at the Si/OP interface and their average density and size. To explain the lifetime difference betweenn‐Si andp‐Si we propose a band bending around OP’s caused by positive fixed charges in the OP’s.

ISSN:0021-8979    

DOI:10.1063/1.336993

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new theory ofa‐Si thin‐film transistor (TFT) operation is presented. In addition to the below‐ and above‐threshold regimes described previously, it predicts two new regimes of operation which occur at very high densities of the induced charge in thea‐Si TFT channel. In a crystallinelike regime the free‐electron concentration exceeds the localized charge concentration at thea‐Si‐insulator interface. In a transitional regime (at lower densities of the induced charge) almost all localized states in the energy gap of amorphous silicon near the interface are filled. In the crystallinelike regime, the field‐effect mobility is close to the band mobility and the operation of ana‐Si TFT is truly similar to the operation of a crystalline field‐effect transistor. Our estimates show that the gate voltage necessary to achieve the crystallinelike regime is about 50 V for ana‐Si TFT with an insulator 1000 A˚ thick and a relative permittivity of approximately 3.9.

ISSN:0021-8979    

DOI:10.1063/1.336994

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The structural, optical, electrical, and optoelectronic properties of magnetron sputtered hydrogenated amorphous‐silicon carbon alloy films have been investigated as a function of sputtering pressure. The optical band gap, the activation energy of dark conductivity, and concentration of hydrogen increase with increasing sputtering pressure. The photoconductivity as well as the dark conductivity shows a maximum against pressure. These results are discussed from the standpoint of the structural and compositional change of the films with sputtering pressure, originating from the change of plasma reaction process composed of the decomposition of methane and the sputtering of silicon.

ISSN:0021-8979    

DOI:10.1063/1.336995

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Single quantum wells of GaAs with barriers of (AlAs)2(GaAs)2ultrathin‐layer superlattices have been fabricated and photoluminescence measurement was performed. The photoluminescence energy was found to change almost linearly against the well width and the photoluminescence linewidth to get smaller with decreasing well width, which is in marked contrast to the case of a usual alloy‐barriered single quantum well. It is indicated that the effective energy gap of the ultrathin‐layer superlattice barrier decreases with the decreasing well width in such a structure.

ISSN:0021-8979    

DOI:10.1063/1.336996

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Gold‐n‐type GaAs Schottky contacts have been fabricated on a single‐crystal part of polycrystalline GaAs with grain size of about 1 cm. The current‐voltage (I‐V) characteristic has been measured over the temperature range 120–380 K. The barrier height is evaluated from the Richardson plot as 0.57 eV, and discussed by taking account of the effects of an interfacial layer between the metal and semiconductor. The capacitance‐voltage (C‐V) characteristic has been measured at 0.1, 1, and 100 kHz over the temperature range 120–500 K. A frequency dispersion is observed in theC‐Vcharacteristic. It is explained by the frequency dispersion in the dielectric constant of the interfacial layer and the capacitive response of trapping states in the interfacial layer and single‐crystal parts of polycrystalline GaAs.

ISSN:0021-8979    

DOI:10.1063/1.336997

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The velocity‐field characteristics of hot electrons moving one dimensionally in the lowest subband of a polar semiconductor quantum‐well wire are obtained on a drifted Maxwellian model and also by the Monte Carlo technique. No negative differential resistance is obtained in contradiction to a previous prediction. The size effects at low temperatures are found to be more significant in the drifted Maxwellian model. Our calculations show that the one‐dimensional (1‐D) mobility for large transverse widths may be higher than the 3‐D mobility.

ISSN:0021-8979    

DOI:10.1063/1.336998

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An alternating terbium‐iron (Tb‐Fe) multilayer structure artificially made in amorphous Tb‐Fe thin films gives rise to excellent magnetic properties of large perpendicular uniaxial anisotropy, large saturation magnetization, and large coercivity over a wide range of Tb composition in the films. The films are superior to amorphous Tb‐Fe alloy thin films, especially when they are piled up with a monatomic layer of Tb and several atomic layers of Fe in an alternating fashion. Small‐angle x‐ray diffraction analysis confirmed the layering of monatomic layers of Tb and Fe, where the periodicity of the layers was found to be about 5.9 A˚. Direct evidence for an artificially layered structure was obtained by transmission electron microscopic and Auger electron spectroscopic observations. Together with magnetic measurements of hysteresis loops and torque curves, it has been concluded that the most important origin of the large magnetic uniaxial anisotropy can be attributed to the Tb‐Fe pairs aligned perpendicular to the films.

ISSN:0021-8979    

DOI:10.1063/1.336999

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The excitation of magnetostatic modes and exchange modes in thin YIG disks has been studied over a wide range of fields. The spectra of films magnetized normally (in magnetic field perpendicular to sample plane) are well described by the model of magnetostatic waves, modified by the exchange interactions. The exchange modes are weak, presumably due to weak pinning at the surfaces of the films. They follow theDk2law. The spectrum obtained in the parallel configuration is not well understood.

ISSN:0021-8979    

DOI:10.1063/1.337000

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The physical and electrochemical coloration characteristics of tungsten oxide films rf sputtered from a compressed powder WO3target have been investigated. Oxide films with 3600–9800 A˚ thickness were deposited on substrates maintained at 200 °C at a total pressure of 0.5–8×10−2Torr in Ar gas or an Ar‐0.5‐50% O2gas mixture. Physical properties of the oxide films depend on the oxygen concentration and total pressure of the sputtering atmosphere. The films prepared at 4×10−2Torr in a mixture of Ar‐0.5‐20% O2gas are transparent and amorphous, and their electrical resistivity ranges from 6.5×108to 2.4×1011&OHgr; cm. The films prepared at pressures between 4 and 6×10−2Torr in an Ar‐50% O2gas mixture are transparent, and have crystallites with a composition of WO3. The films prepared at 1×10−2Torr in a mixture of Ar‐0.5 and 5.0% O2gas are blue colored and transparent, respectively, and these films are crystallites with a composition of WO2.83. Electrochemichromic properties of the rf sputtered tungsten oxide films depend on the film structure, or on the sputtering conditions under which the films are prepared. The amorphous and crystalline WO3films formed at a high total pressure of 3–8×10−2Torr have good electrochemichromic properties and are colored deep blue. However, the crystalline WO2.83films formed at a low total pressure of 0.5–1.5×10−2Torr have poor electrochemichromic properties and are hardly colored. The amorphous oxide films with resistivity of 108–109&OHgr; cm and low density of ∼6.0 g/cm3, formed at a deposition rate higher than ∼100 A˚/min, have very good coloration characteristics. The optical properties and density of the oxide films are also described.

ISSN:0021-8979    

DOI:10.1063/1.337001

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The 1.283‐eV luminescence band observed in GaAs grown from Ga‐rich melts is attributed to a donor–double‐acceptor pair transition which leaves the negatively charged final state of the double acceptor in the 2S3/2excited state. This assignment is shown to be consistent with the estimated energy of such a transition and with the results of Hall effect, infrared absorption, and luminescence measurements. It is proposed that similar emission bands should be observed for other double acceptors and that their observation provides strong evidence for the double‐acceptor nature of such impurities.

ISSN:0021-8979    

DOI:10.1063/1.337023

出版商:AIP    

年代:1986

数据来源: AIP