摘要:

By alternating the deposition of a several‐angstrom‐thick hydrogenated amorphous silicon layer and the exposure to a hydrogen plasma, the structure of the resultant hydrogenated silicon films is varied from device‐grade amorphous to microcrystalline without any change in the film precursors. On the basis of experimental results, the effects of hydrogen atoms reaching the film‐growing surface on the Si‐Si network structure are discussed.

ISSN:0003-6951    

DOI:10.1063/1.102736

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Pseudomorphic InGaAs/GaAs multiple quantum well structures with In contents ranging from 18 to 25% were grown by molecular beam epitaxy and investigated by optical absorption, photoluminescence, and electronic Raman scattering. Sharp exciton peaks with linewidths of ∼3 meV for the first electron to heavy hole transition are observed in the absorption spectra. The electron subband structure was investigated independently by electronic Raman scattering. The transition energies are analyzed using a four‐band effective mass Schro¨dinger equation taking strain into account. A conduction‐band offset ratio &Dgr;Ec/&Dgr;Eg=0.6 is found for all samples independent of In content.

ISSN:0003-6951    

DOI:10.1063/1.102737

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Variations of the GaAs surface conditions and the adsorption of the precursor elements of Cd and Te on the (100)GaAs substrate were studied by x‐ray photoelectron spectroscopy at the initial stage of CdTe growth by organometallic vapor phase epitaxy. The stoichiometry of GaAs substrates was found to recover by annealing in the H2environment (500 °C, 5 min), while the surface was initially in an As‐rich condition after etching with H2SO4:H2O2:H2O (5:1:1). The preferential adsorption of Te on the GaAs surface was also observed. ⟨100⟩ oriented growth was obtained routinely when the GaAs surface was fully stabilized with Te after the H2anneal under the above conditions. ⟨111⟩ oriented growth resulted when dimethylcadmium was first introduced after the anneal.

ISSN:0003-6951    

DOI:10.1063/1.102738

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is shown that the use of hydrogen‐containing gases such as CHF3/H2, CHF3, CH4/H2, and CH4/He in reactive ion etching processes leads to a drastic reduction of the concentration of electrically active acceptors in a thin layer at the surface of highly Zn‐doped InGaAs. This passivation effect leads to strongly nonlinear current/voltage characteristics of nonalloyed Ti/Pt/Au contacts when applied directly on as‐treatedp++‐InGaAs layers. The observed deactivation of acceptors is inferred to be caused by hydrogen since no such an effect was found with the use of hydrogen‐free etching gases.

ISSN:0003-6951    

DOI:10.1063/1.102739

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Optical reflectance difference technique has been applied to semiconductors. It has been demonstrated that differential reflectance spectroscopy (DR) can be equivalent to contactless electromodulation. The measured DR spectra of GaAs are comparable to the published electroreflectance data and show marked improvement in the signal‐to‐noise ratio over the photoreflectance spectra of the same samples. We have used this method to study the confined energy levels in InGaAs/GaAs multiple quantum wells and have found good agreement with the theoretically predicted values. We conclude that DR is a viable alternative to photoreflectance as a contactless electromodulation technique.

ISSN:0003-6951    

DOI:10.1063/1.102740

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Resonant tunneling by fast neutron irradiation with doses from 1×1012to 1×1016n/cm2was studied. We observed that peak and valley positions shifted to higher voltages, and peak‐to‐valley ratios decreased with higher doses in static current‐voltage characteristics. Several models which take into account ionized impurities were used to give consistent explanation to such phenomena.

ISSN:0003-6951    

DOI:10.1063/1.102741

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The mechanism of resonant interband tunneling in polytype heterostructures of GaSb/AlSb/InAs gives excellent peak‐to‐valley current ratios due to the band‐gap blocking of the nonresonant current components. Using InAs as the base in a double‐barrier polytype heterostructure, it is possible to demonstrate resonant tunneling at room temperature through a quantum well as wide as 110 nm. At this width, which is about 20 times larger than that typically used in resonant tunneling diodes in the GaAs/AlGaAs system, the peak‐to‐valley ratio is 44:1 (77 K). Significant negative differential resistance is observed even for 240 nm wells. The projected device response time for a resonant tunneling transistor with a wide InAs quantum base is more than five times faster than for a GaAs device, due to the reduced base resistance.

ISSN:0003-6951    

DOI:10.1063/1.102742

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The redistribution of Be and Mg implants upon post‐implant annealing is studied in order to evaluate the influence of implant damage on the diffusion process. Rapid uphill diffusion is observed in the peak of Mg implants in GaAs, whereas Be implants show only uniform, concentration‐dependent diffusion. This behavior is explained by the substitutional‐interstitial‐diffusion mechanism and computer simulations of damage‐produced point defects. In the region of uphill diffusion, the dopants diffuse from areas of excess interstitials toward areas of excess vacancies. A critical concentration of point defects is necessary to initiate uphill diffusion. Uphill diffusion can be induced in Be implants by co‐implanting with a heavier element such as Ar.

ISSN:0003-6951    

DOI:10.1063/1.102743

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Formation of Schottky barrier contacts ton‐type &bgr;‐SiC(100) was systematically investigated for several metals with various physical and chemical properties. The metals (Pd, Au, Co, Ti, Ag, Tb, and Al) were deposited onto oxygen terminated (∼1 monolayer) surfaces. Metal/&bgr;‐SiC interface chemistry and Schottky barrier height &fgr;Bduring contact formation were obtained by x‐ray photoemission spectroscopy; the corresponding electrical properties of thick contacts were characterized by capacitance‐voltage and current‐voltage methods. The metal/&bgr;‐SiC interface is unreactive at room temperature. X‐ray photoemission spectroscopy and electrical measurements demonstrate that these metal contacts exhibit a wide range of &fgr;B, 0.95–0.16 eV; within this range an individual contact &fgr;Bvalue depends strongly on the metal work function in general accord with the Schottky–Mott limit.

ISSN:0003-6951    

DOI:10.1063/1.102744

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Formation of a thin‐film silicon‐on‐insulator structure by lateral solid phase epitaxy of amorphous Si is described. Thinning of the amorphous Si layer after deposition and densification in an ultrahigh vacuum, prior to solid phase epitaxy, successfully enhances the lateral growth length. In addition, the crystallinity of thin silicon‐on‐insulator layers formed by this technique is found to be better than that achieved by the conventional method.

ISSN:0003-6951    

DOI:10.1063/1.103301

出版商:AIP    

年代:1990

数据来源: AIP