摘要:

The electrical and optical properties of wafer bonded unipolar silicon‐silicon junctions were investigated. The interfaces, bothn‐ntype andp‐ptype, were prepared using wafers with hydrophilic surfaces. The current versus voltage characteristics, the current transients following stepwise changes in the applied bias, and the capacitance versus voltage characteristics as well as the temperature dependence of the current and capacitance were experimentally obtained and theoretically modeled. The proposed model assumes two distributions of interface states, one of acceptors and one of donors, causing a potential barrier at the bonded interface. It is argued that the origins of the interface states are impurities and crystallographic defects in the interfacial region. The capacitance of the bonded structures includes contributions from the depletion regions as well as from minority carriers. When bondedn‐ntype samples were illuminated with light of photon energies larger than the silicon band gap the current across the junction increased. This is caused by the photogenerated increase in the minority carrier concentration in the interfacial region, which results in a lowering of the potential barrier. Illumination ofn‐ntype structures with light of photon energies lower than the band gap caused a considerable photocurrent at low temperatures. In this case the observed behavior cannot be explained by interaction with the interface states. Instead, the mechanism is the change in the occupancy of deep electron traps caused by the illumination. These traps are located in the silicon in a small volume around the bonded interface with energies close to the center of the band gap and with a peak concentration of about 1013cm−3. Impurities present on the silicon surfaces before bonding and impurities gettered to the bonded interface are possible reasons for the increased concentration of deep electron traps in the vicinity of the bonded interface.

ISSN:0021-8979    

DOI:10.1063/1.352172

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The modeling and analysis of electron devices including photovoltaic devices requires the knowledge of the surface recombination velocities at the two surfaces of the wafer along with the bulk lifetime. In this paper, the work of Luke and Cheng [J. Appl. Phys.61, 2282 (1987)] is extended to account for the asymmetric case of different surface recombination velocities at the two wafer surfaces. We present the analysis and discuss experimental procedures to extract the above three parameters. The contactless measurement technique is based on the transient behavior of infrared absorption due to the decay of optically excited excess carriers. In order to determine the surface recombination velocities at both surfaces, the measurements must be made with each side acting as the front surface. An example of parameter extraction is presented.

ISSN:0021-8979    

DOI:10.1063/1.352174

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The phenomenon of electrical degradation in ZnO varistors was studied by application of high‐intensity current pulses. A wave shape of 8×20 &mgr;s and rectangular waves of 1 and 2 ms were used. The degradation was estimated by reference electric‐field variation and by Schottky voltage barrier deformation. The results showed that current pulses reduce both the height and the width of the barrier voltage. It was also observed that the donor densityNddid not change but the surface states densityNsdecreased with degradation.

ISSN:0021-8979    

DOI:10.1063/1.352175

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The electron transmission and bound state properties of a quantum wire with a sharp bend at arbitrary angle are studied, extending results on the right angle sharp bend (the L‐shaped wire). These new results are compared to those of a similar structure, the circular bend wire. The possibility of using a bent wire to perform transistor action is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.352176

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Native surface defects on gallium arsenide are detected by thermally stimulated exoelectron emission measurements. Two emission peaks were identified that were correlated to the AsGaantisite defect. Plasma polymerized polythiophene grown on cleaned gallium arsenide is shown to improve the photoluminescence intensity of gallium arsenide and consequently the exoelectron emission measurements indicated the disappearance of one of the peaks. The results thus confirm the passivation of one of the AsGaantisite defects. The effects are also discussed in view of the low angle x‐ray diffraction spectrum for cleaned and polythiophene treated gallium arsenide. Growth of species involving gallium sulfur and arsenic sulfur were also detected.

ISSN:0021-8979    

DOI:10.1063/1.352150

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The lateral dimensions of resonant tunneling AlGaAs‐GaAs double barrier heterostructures have been restricted by hydrogen plasma exposure. Ohmic contacts to the submicron diodes have been made by solid phase epitaxial growth of Ge on GaAs. The current‐voltage characteristics show a fine structure splitting that is inversely proportional to the lateral size of the diode. The results are interpreted as resonant tunneling through zero‐dimensional states in the quantum box confined by the AlGaAs barriers and a harmonic lateral confining potential.

ISSN:0021-8979    

DOI:10.1063/1.352151

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Real‐space transfer (RST) in three‐terminal devices is analyzed in detail with a Monte Carlo model including size‐quantization effects. A double heterojunction structure is considered with In0.25Ga0.75As as the narrow band gap material. Schro¨dinger’s and Poisson’s equations are solved self‐consistently in one dimension to compute the subband energies and wave functions which are then used to calculate scattering rates for the two‐dimensional electron gas. Electrons are injected at one end of the channel segment and the probability of RST, time required for RST etc. are calculated. Variation of these quantities with respect to longitudinal and transverse electric fields and electron density is studied. We point out that this approach is more relevant to a three‐terminal device like the real‐space transfer transistor than previous approaches which focus on steady‐state velocity‐field characteristics. We also compare the results with a semiclassical model that ignores size‐quantization and observe that quantization favors RST due to the subband structure of the quantum well.

ISSN:0021-8979    

DOI:10.1063/1.352152

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A comparative study of the Schottky barrier height variation on sulfide‐treated GaAs(100) surfaces with low work function metal contacts was made using current‐voltage and capacitance‐voltage measurements. Five different wet chemical sulfide treatments were found to cause little variation in the Sm (0.72 eV) and Mg (0.59 eV) Schottky barrier heights, but caused significant variation in the Al (0.58–0.75 eV) barrier heights when compared to the untreated control diodes. A low temperature (160 °C) anneal was found to cause variation in all of these, uniformly raising the barrier heights of the Sm (+0.07 eV) and Al (+0.04 eV) contacts, and degrading the Mg contacts. These results demonstrate the critical importance of both the reaction specifics and the stability of the interface on the Schottky barrier height.  

ISSN:0021-8979    

DOI:10.1063/1.352153

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have measured the high‐field transport characteristics of pseudomorphic InAsxP1−x/InP (0.3≤x≤1.0) modulation doped heterostructures at 300 and 77 K. The field dependent steady state average velocities increase steadily with increase inx. The maximum velocities that have been measured in InAs/InP are 1.7×107cm/s (2.5 kV/cm) and 3.2×107cm/s (2.2 kV/cm) at 300 and 77 K, respectively. These are the highest velocities measured in any modulation doped heterostructure. The field dependent channel carrier concentration and mobility data indicate that there is very little real space transfer of carriers at high fields and this is confirmed by results from steady state Monte Carlo calculations.

ISSN:0021-8979    

DOI:10.1063/1.352154

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Experiments are reported on two techniques for melt‐texture processing Ba2YCu3O6.5by directional solidification from a semisolid melt containing particles of BaY2CuO5and a copper‐rich liquid. One of these employs an electric resistance furnace with ambient or oxygen enriched atmosphere; the other is a laser‐heated furnace operating at 1.3 atm oxygen. Solidification interface morphologies and other structural features were examined in quenched specimens. Depending on growth rate and temperature gradient, three different types of growth morphologies of the growing 123 phase were observed: ‘‘faceted plane front,’’ ‘‘cellular dendritic’’ or ‘‘equiaxed blocky.’’ The interface temperature decreased markedly with increasing growth rate for the faceted plane front specimens. In the remaining specimens, solidification took place over a range of temperatures. The temperature of the ‘‘root’’ of the solidification front dropped, but temperature of the solidification front ‘‘tip’’ did not. A solidification model is developed and employed to interpret experimental observations. The model assumes limited diffusion of solute in the liquid during the growth of the superconducting phase. The model shows, in agreement with experiment, that growth rate of the low temperature solid phase has a strong effect on ability to obtain the desirable faceted plane front, and that thermal gradient has only a small effect. Interparticle spacing of the high temperature phase, BaY2CuO5, is also predicted to have a strong effect.

ISSN:0021-8979    

DOI:10.1063/1.352155

出版商:AIP    

年代:1992

数据来源: AIP