摘要:

Capacitance‐voltage measurements on GaAs metal insulator semiconductor structures are plagued by charging problems. Additionally, it seems that accumulation cannot be reached owing to Fermi‐level pinning and consequently the insulator capacitance cannot be determined. Furthermore, it is difficult to determine semiconductor characteristics in these MIS structures, which may have changed during annealing. In this paper, a measurement technique is described which eliminates the effect of the charging, allowing the measurement of insulator capacitance, surface potential, and semiconductor doping. This measurement technique is based on the study of transient photovoltage, transient capacitance, and the charging characteristics. This new measurement technique is used to evaluate GaAs MIS diodes and test results are presented.

ISSN:0021-8979    

DOI:10.1063/1.327615

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The importance of specific ion adsorption and surface charge effects in the design and operation of photoelectrochemical (PEC) devices is demonstrated by experimental data on then‐GaAs/electrolyte andn‐Si/electrolyte interface. The electrolyte chosen for the present study was an ambient temperature molten salt comprising mixtures of aluminum chloride andn‐butyl pyridinium chloride in varying molar ratios. A direct correlation between specific adsorption effects and photovoltaic output parameters is presented for then‐GaAs PEC system. Evidence for specific adsorption of Cl−ions in this system is found in the systematic shift observed in flat‐band potentialsVfbtowards negative values with increasing concentration of free Cl−ions in the AlCl3‐BPC electrolyte. The magnitude of the slope ofVfbversuspCl (=−log[Cl−]) plots [∼0.13 V or 2(2.3kT/q) V] is consistent with that expected from Esin‐Markov adsorption behavior. Anomalous PEC behavior is observed at then‐Si/AlCl3‐BPC interface brought about by modifications in electrostatics across the electrode/electrolyte interphasial region. These modifications arise from either specific adsorption effects or by electrodeposition of aluminum on then‐Si electrode surface. Either process results in a net lowering of the band structure inn‐Si on the energy scale relative to the redox levels. An examination of literature data on high‐efficiency PEC systems reveals that similar shifts in the relative positions of the semiconductor energy levels and redox energies may play an important role in ensuring a more favorable photoresponse than that predicted from idealized models.

ISSN:0021-8979    

DOI:10.1063/1.327616

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Vacuum‐ultraviolet light (10.2 eV) generated electrons or holes are injected into the oxide by dc biasing metal‐oxide‐semiconductor Al‐SiO2capacitors with 2800‐A˚ (1000 and 1100 °C) dry oxides annealed in dry oxygen at 600 or 800 °C. The injected charges are trapped in the oxide. The trapped charge density is determined by the capacitance‐voltage method and its location by the photocurrent‐voltage method. The trapped‐hole charge injected under positive dc bias was found to be within 100 A˚ of the oxide‐silicon interface. Trapping kinetic data revealed two donorlike neutral hole traps with hole capture cross sections of 6×10−14and 1×10−15cm2. Both of these traps, after being positively charged by hole capture, were efficient electron traps with an electron‐capture cross section of 3×10−13cm2. An acceptorlike electron trap with an electron‐capture cross section of 1×10−15cm2was also detected which anneals out during 800 °C anneal in dry oxygen. Little increase in the interface‐state density was observed during the charge‐injection and trapping experiments. Analyses of the annealing kinetics of these oxide traps suggest that the larger hole trap is an excess silicon center (trivalent silicon) and the smaller hole trap is an excess oxygen center (nonbridging oxygen).

ISSN:0021-8979    

DOI:10.1063/1.327617

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The rf impedance and the wide‐band response to radiation of a resistively shunted junction (RSJ) model Josephson junction have been measured in the presence of thermal noise, using a phase‐locked‐loop analog of the RSJ model. In the conditions for which analytical calculations are valid there is good agreement between the theory and the analog. When the RSJ model is shunted with a capacitance, a plasma type resonance can occur in the rf impedance when the junction is biased in the supercurrent (in‐lock). When thermal noise is present, this plasma resonance can also occur when a nonzero average voltage is generated across the junction. We found that in this case a resonance also occurs in the wide‐band response to radiation. This resonance takes place at a frequency that can be identified as the attempt frequency, with which the junction attempts to escape the phase locked condition in which it exists for a fraction of the time even though the average voltage across the junction is nonzero. The average lifetimes of the junction in lock &tgr;in(?=0) and out of lock &tgr;out(?=?out) were also measured in the presence of thermal noise. &tgr;inis in good agreement with existing theory and &tgr;outis derived from the measurements.

ISSN:0021-8979    

DOI:10.1063/1.327618

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The anomalous volume contraction &ohgr;a(T) of Fe‐Ni and Fe‐Pt Invar alloys were analyzed in terms of the Gru¨neisen equation using the experimental data of thermal expansion coefficient. It was found that &ohgr;a(T) increases with increasing Fe composition or temperature and remains nonzero even above the Curie point &Vthgr; ffor both the Invar alloys. The susceptibility of Fe‐Ni alloys and the magnetization of Fe‐Pd alloys were measured. The magnetic anomalies of Invar alloys are summarized. A calculation by molecular field theory in terms of a high and low spin state transition model can well explain the anomalous isothermal magnetization curve and the anomalous volume contraction as well as instability of ferromagnetism, where the center of the low spin state has higher energy than the high spin state at high temperatures and the distribution of low spin state energy and the exchange field of the high spin state were considered. From the x‐ray diffraction experiments at low temperatures, an anomalous random static displacement (?2s)1/2was obtained after subtracting the mean‐square displacement of the lattice vibration of Fe‐Ni Invar. Such a displacement may come from the mixed state of high and low spins.

ISSN:0021-8979    

DOI:10.1063/1.327619

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Optical constants of amorphous Se1−xTexfilms have been measured for 0⩽x⩽0.45 at wavelengths from 0.35 to 2 &mgr;m using both an ellipsometer and a spectrophotometer. The results show that the optical transmission cutoff wavelength, the refractive index, and the extinction coefficient vary linearly withx(the Te content). The optical constants are dispersive. The dispersion is attributed to the optical transition of electrons from the valence band to the conduction band. All results can be consistently explained on this basis. The substitution of Te atoms for Se atoms in Se1−xTexfilms increases the density and enhances the tailing of the localized states into the mobility gap, thus resulting in the change of optical constants withxin Se1−xTexfilms.

ISSN:0021-8979    

DOI:10.1063/1.327620

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Optical homogeneous linewidths of the4F3/2–4I9/2transition of Nd3+in oxide and fluoride based glasses are measured for host composition ranging from simple binary to multicomponent glasses. Homogeneous linewidths at 300 K exhibit a broad range of values, varying by approximately a factor of 4. The ratio of homogenous to inhomogeneous linewidth also varies over a broad range, from 0.16 for a sodium barium borate glass to 1.86 for a rubidium phosphate glass. In addition, the homogeneous linewidth is inversely dependent to the ∼2.5 power of the velocity of sound from host to host. This dependence is not predicted by existing theories of the line broadening process.

ISSN:0021-8979    

DOI:10.1063/1.327621

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The photoluminescence of Ge‐doped AlxGa1−xAs grown by liquid phase epitaxy (LPE) was investigated. The ionization energy of Ge, determined from the photoluminescence spectra, has a strong relation to the Al composition. This cannot be explained by a simple effective mass‐like expression. The broad emission band with a peak at about 1.5 eV, which has been observed by several investigators, was studied further. The intensity of the emission band increased as Ge or as implanted O concentration increased. The peak energy shifted toward higher energy as excitation intensity increased. The paper suggests that this emission band is caused by O donor‐Ge acceptor pair recombination.

ISSN:0021-8979    

DOI:10.1063/1.327622

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Previous attempts to understand the mechanism responsible for the 1.4‐eV luminescence in solution‐grown CdTe:In were inconclusive because the measured combinations of injection level dependence, frequency response, and temperature dependence did not clearly indicate whether the transition originated from a band state or from a localized level associated with a compact complex. This paper reports the discovery of CdTe:In material in which temperature‐dependence data show that the 1.4‐eV luminescence transition cannot originate at a band edge. However, the spectrum, injection level dependence, and frequency response of the 1.4‐eV luminescence in the present material do not differ greatly from corresponding measurements on previous materials. The new data are presented in detail and include the first extensive measurements of the thermal broadening of the 1.4‐eV luminescence.

ISSN:0021-8979    

DOI:10.1063/1.327623

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electromigration velocities of a liquid gallium inclusion in single‐crystal silicon follow an Arrhenius relationship with temperature. The activation energy is 14.5 kcal/mol and the preexponential factor is 2.1×10−5cm3/C. Electromigration velocities are linearly proportional to the applied electric current density. Ga inclusions electromigrate towards the cathode at all temperatures. The electron‐atom momentum exhange is the principal electromigration driving force. Peltier‐induced temperature‐gradient zone melting contributes less than 1% of the observed electromigration velocity. Current funneling into the gallium‐doped redeposited‐silicon train behind the electromigrating inclusion can increase the current density passing through the inclusion by up to a factor of 10. At temperatures below 500 °C, current diversion by rectification by thep‐I junction between the doped inclusion trail and the parent silicon crystal inhibits gallium‐inclusion electromigration.

ISSN:0021-8979    

DOI:10.1063/1.327624

出版商:AIP    

年代:1980

数据来源: AIP