摘要:

We use absorption, photoluminescence, and x‐ray diffraction spectra of two GaAs/AlAs type II heterostructures, whose GaAs well thicknesses differ by &bartil;4 A˚ to obtain a direct measurement of the individual quantum confinement energy shifts of the heavy hole, light hole, and electron levels. We find that excitonic absorption linewidths are dominated by inhomogeneous broadening that arises from half‐monolayer well‐thickness fluctuations. For self‐consistency these shifts are applied to separately determine the individual valence‐band and conduction‐band offsets.

ISSN:0003-6951    

DOI:10.1063/1.103448

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Low‐temperature ion beam mixing rates for Ni‐Ti, Zr‐Ni, and Pd‐Ni bilayers significantly exceeded binary collision estimates, and appeared quite sensitive to thermodynamic driving forces. In the absence of a temperature dependence such a behavior is commonly ascribed to interdiffusion within thermal spikes. However, the Ni‐Ti mixing rate was seen to vary linearly with nuclear damage energy for irradiation with 600 keV Xe, Kr, or Ar, 300 keV Ne or N, or 200 keV N ions, or 1 MeV Au ions (literature value). This excludes overlapping thermal spikes. An expression was derived for mixing due to nonoverlapping thermal spikes, but this could also not explain our results.

ISSN:0003-6951    

DOI:10.1063/1.103449

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A lateral silicidation problem has been found in the conventional self‐aligned titanium disilicide (TiSi2) process for making ohmic contacts to heavily dopedp‐type (p+) silicon in the submicron domain. Two solutions curtailing the lateral Si migration and the resulting lateral silicide formation are presented: an additional low‐temperature nitrogen anneal and an interfacial carbon layer. Excellent ohmic contacts with a minimum area of 0.06 &mgr;m2and a spacing of 0.2 &mgr;m are demonstrated with both solutions.

ISSN:0003-6951    

DOI:10.1063/1.103450

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Atomically sharp tungsten tips (<20 A˚) have been grown on a silicon substrate by chemical vapor reaction of WF6with atomically sharp preformed silicon tips. Transmission electron microscope studies show that a thickness of about 50 A˚ of tungsten is optimum for complete coverage of silicon while retaining atomic sharpness at the tip. The tungsten is nearly amorphous and is porous. These tips have potential applications in vacuum microelectronics as electron emitters and can also be used as electronic and magnetic microsensors and probes.

ISSN:0003-6951    

DOI:10.1063/1.103451

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin‐film transistors were thermally annealed while a bias voltage was applied to the gate electrode. The transfer characteristics were then measured, and the density of states distributions derived by field‐effect analysis. The results indicate that theequilibriumdistribution and number of defects in the transistor channel region depend on the position of the Fermi energy during annealing. Thus the density of states can be increasedordecreasedin parts of the band gap. A high Fermi energy during annealing results in few states high in the gap and more states low in the gap. The reverse is true for annealing while the Fermi energy is low. This is consistent with the defect pool model for silicon dangling bond states and suggests that most deep states are part of the defect pool.

ISSN:0003-6951    

DOI:10.1063/1.103452

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Infrared radiation at wavelengths of 1–2 &mgr;m has been detected in a new device labeled the layered internal photoemission sensor. The device structure, which is grown by molecular beam epitaxy, incorporates epitaxial CoSi2particles with dimensions of 10–50 nm. Radiation absorbed by these particles photoexcites carriers into a surrounding single‐crystal silicon matrix. A peak quantum efficiency of 1.3% is measured, which is approximately six times higher than in planar CoSi2Schottky diodes with 5 nm silicide thickness.

ISSN:0003-6951    

DOI:10.1063/1.103453

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new approach to the design of a Si‐based infrared detector is demonstrated, based on internal photoemission over a Si1−xGex/Si heterojunction barrier. The heterojunction internal photoemission device structure is grown by molecular beam epitaxy (MBE). The detector requires a degenerately dopedp+‐Si1−xGexlayer for strong infrared absorption and photoresponse. Doping concentrations to 1020cm−3are achieved using boron from a HBO2source during MBE growth of the Si1−xGexlayers. The photoresponse of this device is tailorable, and most significantly, can be extended into the long‐wavelength infrared regime by varying the Ge ratioxin the Si1−xGexlayers. Results are obtained withx=0.2, 0.28, 0.3, and 0.4 on patterned Si (100) substrates. Photoresponse at wavelengths ranging from 2 to 10 &mgr;m is obtained with quantum efficiencies above ∼1% in these nonoptimized structures.

ISSN:0003-6951    

DOI:10.1063/1.103454

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using identical Ga flux density, we have measured the growth rate difference between GaAs and GaSb. The large discrepancy of 15% seems to suggest a change in the sticking coefficient of Ga when different group V species are involved. However, when lattice parameters are taken into account correctly, the discrepancy appears to be a natural consequence because fewer Ga atoms are needed to complete a monolayer on the GaSb surface. Similar results are also observed for the growth of Al(Sb,As) and In(Sb,As). This points to the possible systematic error in the estimation of ternary composition, such as InGaAs, by adding the growth rates of binary constituents InAs and GaAs without correction for change in lattice constants.

ISSN:0003-6951    

DOI:10.1063/1.103455

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Synchrotron radiation soft x‐ray photoemission spectroscopy was used to investigate the native oxide ofn‐type single‐crystal CuInSe2. Photoemission measurements were acquired on the oxide surface before and after removal using sputter etching. Observed changes in the valence‐band electronic structure as well as changes in the In 4dand Se 3dcore lines were correlated with the interface chemistry at the oxide/CuInSe2interface. These results show the native oxide to be composed of an In2O3outer layer (no SeO2) with an additional Cu2Se interface layer.

ISSN:0003-6951    

DOI:10.1063/1.104122

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This letter describes our initial results of using a theoretical determination of the proximity function and an adaptively trained neural network to proximity correct patterns written on a Cambridge electron beam lithography system. The methods described are complete and may be applied to any electron beam exposure system that can modify the dose during exposure. The patterns produced in resist show the effects of proximity correction versus noncorrected patterns.

ISSN:0003-6951    

DOI:10.1063/1.103456

出版商:AIP    

年代:1990

数据来源: AIP