摘要:

The interfacial reactions between thin films of cobalt and germanium and (001)‐oriented GaAs substrates in two configurations, Co/Ge/GaAs and Ge/Co/GaAs, were studied. The microstructure and phase formation, as analyzed by transmission electron microscopy, x‐ray diffraction, and Auger electron spectroscopy, were correlated with the electrical properties of these contacts, as determined by current‐voltage and capacitance‐voltage measurements. At low temperatures, 250≤T<325 °C, the only reaction that was monitored was the formation of Co5Ge7at the outer interface, while the GaAs substrate remained intact. The growth of Co5Ge7was diffusion limited with an activation energy of ∼0.7 eV. At the temperature range of 325–400 °C for both metalizations epitaxial Co2GaAs was formed on top of the GaAs beneath the Co5Ge7layer. For the Ge/Co/GaAs metalization this was accompanied (at 400 °C) by solid‐phase epitaxial growth of Ge precipitates on the GaAs surface. Contacts produced in this annealing regime were rectifying with nearly ideal thermionic emission behavior. The Co2GaAs phase was unstable at higher temperatures (500–600 °C), and the reaction products were two ternary phases, with compositions of Co2GeGa and Co2GeAs. These compounds were spatially separated—the Co2GeGa layer on top of the Co2GeAs phase. Contacts produced at the high‐temperature regime (>400 °C) had very low effective barriers and on ann+GaAs substrate became ohmic.

ISSN:0021-8979    

DOI:10.1063/1.346571

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Liquid‐phase epitaxy allows SiGe alloys of good quality to be grown on Si substrates. We deposit single crystalline,n‐type Si1−xGexfilms with 0.7<x<1 from Bi solutions on (111)‐oriented Si. The films are up to several &mgr;m thick and are uniform in thickness and in composition. The analysis by x‐ray diffraction indicates good crystallinity and a dislocation density below 5×107cm−2. Photoluminescence measurements show well‐resolved peaks with the smallest linewidths reported so far for epitaxial SiGe. Hall‐effect measurements yield electron concentrations around 1×1016cm−3and room‐temperature electron mobilities of up to 340 cm2/V s.

ISSN:0021-8979    

DOI:10.1063/1.346572

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The growth process in the initial stage of growth of Ge films on (811)Si substrate surfaces by GeH4source molecular‐beam epitaxy has been studied byinsitureflection high‐energy electron diffraction observation. It has been found that a strained film by the monolayer overgrowth mode is formed initially with an epitaxial relationship of the parallel orientation, and that plate‐shaped Ge islands with (811) facets are grown early in the growth, but that the predominant facet changes to {311} and the (100) planes with further growth. These growth processes are similar to those of Ge films on (100)Si surfaces reported previously. It is concluded that Ge islands with {811} facets are energetically stable in the initial stage of the island growth on the (811)Si surfaces as well as on the (100)Si surfaces.

ISSN:0021-8979    

DOI:10.1063/1.346573

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A variation on molecular beam epitaxy (MBE), called van der Waals epitaxy, is described where a material with primarily two‐dimensional (2D) bonding is grown on a substrate which also has a 2D structure. Lattice matching difficulties, which limit the choice of materials in MBE of 3D systems, are circumvented since the interlayer bonding is from weak van der Waals interactions. The title system shows a lattice mismatch of 10% yet high quality epitaxial films can be grown. The films were characterizedinsituwith reflection high energy electron diffraction, Auger electron spectroscopy, and low energy electron loss spectroscopy. Additional characterization after exposure to ambient by x‐ray photoelectron spectroscopy, low energy electron diffraction, transmission electron microscopy confirmed the highly ordered nature of the films. Scanning tunneling microscopy provided real space images of the morphology of the epitaxial layer and showed unusual structures attributed to lattice mismatch.

ISSN:0021-8979    

DOI:10.1063/1.346574

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The crystal‐field splittings recently observed in the Er‐related optical absorption spectra of ErAs films grown on GaAs by molecular‐beam epitaxy are further investigated with respect to their applicability in characterizing strain accommodation in ErAs/GaAs multilayer structures. Rutherford backscattering axial channeling measurements are used to directly assess strain accommodation in the epitaxial films. The crystal‐field splittings observed in room‐temperature absorption spectra of samples containing thick strain‐relieved ErAs layers are consistent with the cubic (Oh) symmetry expected for the Er lattice site in unstrained ErAs. In sharp contrast, a multilayer structure containing two‐monolayer‐thick, coherently strained ErAs layers shows pronounced changes in the energies, linewidths, and relative intensities of the crystal‐field‐split spectral lines, as well as the appearance of additional weak absorption lines. This behavior is attributed to strain‐induced distortion of the crystal field in which the rare‐earth ions reside. The relative influence of hydrostatic and uniaxial strain components on the optical spectra is discussed.

ISSN:0021-8979    

DOI:10.1063/1.346545

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The growth and optical band gaps of heteroepitaxial layers of the ternary In1−xGaxSb [0≤x≤1] on (100)GaAs is reported. The epilayers, prepared by metalorganic magnetron sputtering using trimethyindium, trimethylgallium, and a sputtered antimony beam, showed good structural and surface morphologies despite a lattice mismatch between substrate and epilayer of 9%–14%. Secondary ion mass spectrometry analysis indicated a background carbon level in proportion to the gallium concentration. The high levels of carbon were not present in the InSb layers prepared using TMI. All films showed optical absorptions characteristic of direct gap semiconductors. The bowing parameter for the system is somewhat lower than that observed for the corresponding bulk material and may be related to compressive stress in the layers.

ISSN:0021-8979    

DOI:10.1063/1.346546

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A technique is developed to control the chemical reactivity of a silicon single‐crystal surface through chemical modification with atomic hydrogen. The reactivity of the reconstructed single‐crystal surface prepared by high‐temperature treatment in an ultrahigh vacuum is significantly decreased by capping the dangling bonds of top‐layer silicon atoms with hydrogen atoms. The Si—H bonds on the hydrogenated surface are found to be much more stable against oxidation than the Si—Si back bonds. The hydrogen‐passivated silicon surface is reactivated by electron beam irradiation. An ultrathin oxide layer pattern can be prepared using preferential oxidation of the area reactivated by a focused electron beam.

ISSN:0021-8979    

DOI:10.1063/1.346521

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using controlled N2/Ar sputtering gas mixtures, rf‐sputtered films were prepared from Fe, Ni, and Ni81Fe19targets, and their structure and orientation were studied by x‐ray diffraction. When no N2was introduced during sputtering, all the films were oriented in the highest density planes; i.e., in (110), (111), and (111) for &agr;‐Fe, Ni, and &ggr;‐Ni81Fe19, respectively. With increasing N2introduction, however, the orientation shifted to lower density planes, and eventually nitrides were formed. Multilayer films of metal and nitride were prepared with the Ni81Fe19target by repetitive supply of N2for short periods during sputtering. Strong orientation effects were observed depending on the number of layers grown. In addition, the x‐ray diffraction of these films presented evidence of epitaxial growth of the nitrides (Ni,Fe)4N on the alloy layers.

ISSN:0021-8979    

DOI:10.1063/1.347176

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thermally stimulated conductivity (TSC) data on high‐resistivity,p‐type CdTe single crystals are presented. The CdTe samples under study were either nominally undoped or doped with Mn or Fe. Deconvolution and peak fitting analysis of the TSC curves consistently revealed the presence of traps at approximatelyEv+0.16,Ec−0.24,Ev+0.23,Ev+0.32,Ev+0.39,Ev+0.40, andEv+0.47 eV in etched samples corresponding to TSC maxima at approximately 95, 110, 120, 145, 165, 170, and 190 K, respectively. An additional TSC peak, believed to be related to surface damage caused by mechanical polishing, is observed at approximately 105 K corresponding to electron traps atEc−0.21 eV. The evidence indicates that the TSC curve from 80 to 200 K may be best described as a superposition of first‐order (slow‐retrapping) processes. Frequency factors and capture cross sections are calculated as temperature‐dependent power‐law functions. Some of the traps have been associated with particular defect structures, however, no clear correlation with the presence of Mn or Fe is observed.

ISSN:0021-8979    

DOI:10.1063/1.346522

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper relates different points concerning defect levels and lattice defects in CuInSe2and the I‐III‐VI2compounds. First, we review the main levels observed. Second, we propose a hypothesis concerning the electrical compensation processes acting in the I‐III‐VI2materials. Third, we discuss the nature of the defects responsible for the levels, and improve interpretations, by carrying out the deformation potential in antisite defects. Especially, these calculations reinforce the idea that the ‘‘hydrogenic‐type’’ acceptor observed in the I‐III‐VI2materials must rather be attributed to the Cu or Ag vacancy than to an antisite defect.

ISSN:0021-8979    

DOI:10.1063/1.346523

出版商:AIP    

年代:1990

数据来源: AIP