摘要:

Zinc blende and wurtzitic GaN films have been epitaxially grown onto (001)Si by electron <m1;&1p>cyclotron resonance microwave plasma‐assisted molecular beam epitaxy, using a two‐step growth process. In this process a thin buffer layer is grown at relatively low temperatures followed by a higher temperature growth of the rest of the film. GaN films grown on a single crystalline GaN buffer have the zinc blende structure, while those grown on a polycrystalline or amorphous buffer have the wurtzitic structure.

ISSN:0003-6951    

DOI:10.1063/1.106309

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The distribution of Si dopant at the Au/GaAs interface after heat treatment has been studied using spatially resolved secondary‐ion mass spectrometry. Previously it has been shown that heat treatment changes as deposited Au thin film from Schottky contacts to ohmic contacts. The present study shows that the transition to an ohmic contact results from segregation of dopants in areas where GaAs is decomposed by reacting with the Au overlayer. Thus the ohmic contact is spatially very inhomogeneous at the metal/semiconductor interface. The mechanism leading to concentrations of the Si and nonuniform ohmic contacts is discussed, and segregation to the solid during decomposition of the GaAs is the most likely mechanism.

ISSN:0003-6951    

DOI:10.1063/1.106310

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The early stage of the growth of plasma deposited amorphous silicon (a‐Si:H) on glass substrates is investigated byinsituinfrared phase modulated ellipsometry in the silicon–hydrogen stretching mode region. Analysis of the spectra provides unprecedented sensitivity and quantitative information on the film evolution. In particular SiH, SiH2, and SiH3bonds are identified in 5–20 A˚ thick samples. The bond densities of SiH and SiH2in thin films are estimated. After the interaction with the substrate,a‐Si:H films grow beneath a hydrogen rich overlayer containing SiH2and SiH3bonds. At 250 °C the thickness of this overlayer is compatible with one monolayer. The hydrogen‐passivated surface ofa‐Si:H is then weakly reactive.

ISSN:0003-6951    

DOI:10.1063/1.106311

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Epitaxial &agr;‐Fe films have been grown on HF cleaned Si(111) substrates at 30 °C by electron beam evaporation in an ultrahigh vacuum environment to a thickness of several thousands of Angstroms. Conventional &thgr;−2&thgr; x‐ray diffraction shows that only the Fe(222) peak is present, indicating that the films are oriented with the Fe(111) plane parallel to the Si(111) plane. Transmission electron microscopy shows that the Fe[11¯0] direction is parallel to the Si[11¯0] direction in the plane of the substrate.

ISSN:0003-6951    

DOI:10.1063/1.106312

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The photoconductive response of hydrogenated amorphous silicon (a‐Si:H)p‐i‐ndiodes has been investigated under conditions of low‐temperature operation. We show that cooledp‐i‐ndiodes exhibit an enhanced infrared response when operated under forward bias conditions. The induced IR response is of the order of 10−3A/W, extending out to wavelengths of about 2–3 &mgr;m with the long wavelength cutoff being determined by the properties of the glass/indium–tin–oxide entrance window. We propose that the IR photoeffect is due to the re‐excitation of band‐tail trapped excess carriers injected into the localized conduction and valence band tail states in the vicinity of then+‐ andp+‐contact regions.

ISSN:0003-6951    

DOI:10.1063/1.106313

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Epitaxial growth of a GaAs film with a fine pattern is realized by Ar ion laser irradiation during metalorganic molecular beam epitaxy. Corrugation patterns with 0.85 and 4 &mgr;m pitch are successfully grown on a GaAs substrate using a holographic interference technique, i.e., irradiation of the interference fringe pattern of two laser beams. The cross‐section profile of the pattern is similar to a sinusoidal curve, expected from laser power distribution of interference. Vibration of a substrate during epitaxial growth is discussed comparing obtained pattern height to the theoretical one.

ISSN:0003-6951    

DOI:10.1063/1.106314

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The presence of a free hole gas and its coupling to longitudinal optical phonons were established with Raman spectroscopy in Li doped ZnSe layers grown by molecular beam epitaxy on GaAs substrates. The phonon spectra shift to higher frequencies and broaden with increasing acceptor concentration and temperature, according to the behavior of coupled phonon‐plasmon modes. Values for the concentration and mobility of the holes were obtained from the analysis of the spectral line shapes. They agree with determinations by other methods. A linear relationship was found between the spectral broadening and the hole concentration.

ISSN:0003-6951    

DOI:10.1063/1.106315

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have studied the growth of GexSi1−xalloys on Si(110) surfaces. For this growth normal, there are only two inclined {111} glide planes intersecting the interfacial plane. Both intersections are along the same in‐plane [11¯0] direction, thus classica/2⟨110⟩{111} glide misfit dislocations can form along only one interfacial direction. This produces an orthorhombic unit cell following strain relaxation by misfit dislocations. At sufficiently high stresses, previously unobserved misfit dislocation structures are activated. The critical thickness for misfit dislocation introduction is found to be shifted to lower Ge compositions with respect to growth on the (100) surface, consistent with a higher angular factor resolving the interfacial component of the dislocation Burgers vector in the (110) system.

ISSN:0003-6951    

DOI:10.1063/1.106316

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Operation of a novel three‐terminal resonant tunneling device which consists of an AlGaAs/GaAs modulation‐doped structure grown on top of an AlAs/GaAs double‐barrier resonant tunneling heterostructure has been demonstrated. In this device, the drain‐to‐source voltage is used to directly control the bias across a resonant tunneling structure, while the gate voltage controls the number of carriers available for the tunneling process by modulating the density of carriers in a two‐dimensional electron gas. Device operation is demonstrated at 80 K as well as room temperature with peak current densities of 420 A/cm2and peak‐to‐valley ratios as high as 5:1. Operation into the hundred gigahertz range is predicted for an optimized device structure.

ISSN:0003-6951    

DOI:10.1063/1.106317

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the observation of strong photoinduced intersubband absorption in a lattice‐matched In0.53Ga0.47As/InP multiquantum well structure. The absorption, which is induced by optical pumping with an above gap light is polarized along the growth direction and is assigned to the transition from the first to the second subband in the conduction‐band quantum well. The measured intersubband transition energy is in very good agreement with an effective‐mass‐approximation model including nonparabolicity effects. Assuming a linear dependence of the electron effective mass on the energy, we find a nonparabolicity parameter of 1.35±0.25 eV−1for the In0.53Ga0.47As well.

ISSN:0003-6951    

DOI:10.1063/1.106318

出版商:AIP    

年代:1991

数据来源: AIP