摘要:

We have studied the correlation length (&Lgr;) of interface roughness in GaAs/AlAs quantum wells (QWs) prepared by molecular beam epitaxy (MBE). It is found that the mobility of two‐dimensional electrons in very thin selectively doped GaAs/AlAs QW structures is substantially enhanced when the bottom AlAs barrier layer is prepared by alternate beam MBE and/or by the use of superlattice buffer layer below the QW. By measuring the electron concentration dependence of mobility and comparing with the theory of interface roughness scattering, we have found that &Lgr; of the bottom (GaAs‐on‐AlAs) interface of the QW gets as large as 200–300 A˚, when prepared by the modified growth technique, which is about three times as large as that (∼70 A˚) by conventional MBE.

ISSN:0003-6951    

DOI:10.1063/1.104077

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We found that the radiation damage induced in a SiO2/Si system during plasma processing depends strongly on the specimen temperature. The surfaces of the SiO2have been exposed to a microwave plasma at different temperatures and the resultant damage has been evaluated by capacitance‐voltage (C‐V) measurements. The flatband voltage shift (&Dgr;VFB) for the specimen exposed to the plasma at 126 K has been found to be only 1/3 of that at 300 K. In case of vacuum ultraviolet photon irradiation through a thin Al film, the &Dgr;VFBfor the irradiation at 126 K has been only 1/5 of that at 300 K. It is believed that this lower plasma‐induced damage at the lower temperature is due to the small mobility of hole in SiO2at lower temperatures. Plasma etching at low temperature has the advantage of low damage generation in the SiO2/Si structures.

ISSN:0003-6951    

DOI:10.1063/1.104133

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial ReSi2thin films grown on Si (100) substrates were analyzed at room temperature by MeV 4He backscattering and channeling spectrometry. The minimum yield of [100] axial channeling increases with increasing exposure of the ReSi2sample to the analyzing He beam. This means that ReSi2suffers irradiation damage induced by a MeV 4He beam. The damage in the film induced by a beam incident along a random direction is about one order of magnitude larger than that induced by a beam with an aligned incidence, indicating that the damage is mainly generated by elastic collisions of nuclei. The experimentally measured defect concentration produced at 300 K by a beam of random incidence is compared with the theoretically estimated one produced at 0 K in an amorphous target. The agreement is fairly good, suggesting that the defects are stable at room temperature.

ISSN:0003-6951    

DOI:10.1063/1.104134

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Nitridation of titanium layer is performed in a high‐pressure (5.9 kg/cm2) ammonium (NH3) ambient. Although the nitridation of titanium surface does not occur at 700 °C in an atmospheric pressure, it does occur at 650 °C in an ammonium pressure of 5.9 kg/cm2. Nitridation temperature can be lowered by 100–150 °C with an increase in ammonium pressure from 2.0 to 5.9 kg/cm2. Thickness of titanium nitride layer increased markedly with increasing ammonium pressure. This is due to the enhancement of the chemical reaction of titanium with ammonium gas by the increase of pressure. The thickness increases with an increase of nitridation temperature. The thickness of the titanium silicide layer formed by the silicidation reaction between titanium and the silicon wafer is reduced with the increase in ammonium pressure.

ISSN:0003-6951    

DOI:10.1063/1.104078

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the first demonstration of ZnSe metal‐semiconductor field‐effect transistors. These new devices were fabricated fromn‐type Cl‐doped epitaxial ZnSe layers grown by molecular beam epitaxy on (100) oriented semi‐insulating Cr‐doped GaAs substrates. Epitaxial layers with room‐temperature carrier concentrations of 1.6×1017cm−3and electron mobilities ranging from 400 to 500 cm2/V s were used for device fabrication. Au was used as a Schottky gate contact. Either In or a multilevel metallization scheme using Cr and In was employed for the source and drain ohmic contacts. Depletion‐mode transistor operation was observed for structures with 5 and 100 &mgr;m gate lengths and varying gate widths. The 5 &mgr;m gate length by 200 &mgr;m gate width device structures exhibited transconductances of 0.5 mS/mm.

ISSN:0003-6951    

DOI:10.1063/1.104079

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Time‐resolved, space‐imaged Raman spectroscopy has been employed to study the transport properties of excitons in GaAs quantum wells. For an injected exciton density ofnex&bartil;1.5×1011cm−2, the experimental results show that exciton transport can be well described by a simple diffusion model. Based on the temperature and well‐width dependence of the deduced diffusion constant, we demonstrate that at low temperatures, i.e.,T≤60 K, the transport of excitons in GaAs quantum wells is primarily governed by two dominant mechanisms: acoustic phonon scattering and interface roughness scattering.

ISSN:0003-6951    

DOI:10.1063/1.104080

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A semi‐infinite stratified multiquantum well structure with the boundary connected to a homogeneous medium is suggested. Electronic surface states are found to exist under certain conditions. These surface states have an interesting feature that the eigenenergy may even exceed the confinement potential of the periodic substrate. Possible application of this structure in optoelectronic devices is discussed.

ISSN:0003-6951    

DOI:10.1063/1.104081

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have developed a complete lithographic process combining focused ion beam writing, dry etching, and molecular beam epitaxy forinsitupreparation of buried InP‐based microstructures. A focused ion beam is used to locally remove an ultrathin oxide imaging layer growninsituon the surface of InP. The pattern is transferred into the underlying semiconductor by free Cl2etching with the patterned oxide layer acting as an etch mask. After removal of the oxide mask, GaInAs/InP heterostructures with excellent morphology and high luminescence efficiency can be grown on the patterned substrate. The entire process of mask formation, lithography, and regrowth can be carried outinsiturepeatedly, and used for creating fully buried microstructures.

ISSN:0003-6951    

DOI:10.1063/1.104082

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin (∼18 nm) polyoxide films have been grown on phosphorus‐implanted polycrystalline silicon (poly‐Si) by rapid thermal oxdiation (RTO). With an emphasis on the bias polarity dependence, we have studied the electrical characteristics of polyoxides, such as leakage current, breakdown field, and charge trapping. In comparison with polyoxides grown in conventional furnace, RTO polyoxides exhibit a significantly reduced leakage current. In addition, the dielectric breakdown strength and breakdown field distribution have been improved. When electrons were injected from the top poly‐Si/SiO2interface, RTO polyoxide shows a reduced trapping rate. However, when electrons were injected from the SiO2/bottom poly‐Si interface, RTO polyoxide shows an increased trapping rate.

ISSN:0003-6951    

DOI:10.1063/1.104135

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Coherent ballistic transport through a cavity in a quantum electron waveguide is examined. Electrons passing through the cavity excite vortices in the current density in the cavity. The circulating currents may be larger than the current in the waveguide leads. Vortex excitations are possible even when the incoming current is totally reflected and no net current passes through the cavity.

ISSN:0003-6951    

DOI:10.1063/1.104083

出版商:AIP    

年代:1990

数据来源: AIP