摘要:

Refractive indices of InGaAs/InAlAs multiquantum‐well layers grown by molecular‐beam epitaxy are determined by reflectance measurements as a function of photon energy and barrier width, i.e., average Al content. These results are well explained by the single‐oscillator model; oscillator energy (E0) and dispersion energy (Ed) values vary linearly with average Al content. These values are, however, found to differ from the values obtained by the linear approximation of the parameters for binary alloys. Discussion of this discrepancy is also presented.

ISSN:0021-8979    

DOI:10.1063/1.340267

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Low‐temperature photoluminescence (PL) related to Co deep impurities in In1−xGaxP (0.74≤x≤1) and GaAs1−xPx(0.65≤x≤1) alloys has been studied. Broad PL bands with some structures have been observed in the 2.3‐&mgr;m region for both the alloys. The results of time‐resolved PL measurements have shown that the PL bands are due to the intracenter transitions4T2(4F)→4A2(4F) in a substitutional Co2+ion in the zinc‐blende lattices. These Co‐related PL spectra have been analyzed in terms of the local atomic arrangements around the Co luminescent center. As a result, it has been found that these Co‐related PL spectra in InGaP and GaAsP alloys are composed of several bands closely related to the local arrangement of atoms around the Co center.

ISSN:0021-8979    

DOI:10.1063/1.340268

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

GaAs epitaxial layers (0.5 &mgr;m<d<4 &mgr;m) were grown by molecular‐beam epitaxy (MBE) on (100) Si substrates (2° off in ⟨011⟩ direction) by using the two‐step growth mode. The structural properties of the grown films (lattice constants, misorientation, crystal quality) have been measured by high‐resolution double‐crystal x‐ray diffraction. The GaAs layers are under biaxial tensile strain at temperatures below the growth temperature because of the difference in thermal expansion coefficients of GaAs and Si. With the use of temperature‐dependent photoluminescence and excitation spectroscopy, the band edges as well as the dominant near‐band‐edge recombination processes have been determined. Excitonic resonances are clearly observed in the excitation spectra. The strain splitting between the heavy‐ and light‐hole valence bands amounts to 13 meV at 4.5 K. The dominant low‐temperature luminescence line at 1.489 eV is assigned to exciton‐related recombination processes. In addition to the band‐to‐carbon acceptor (e,A0C) recombination at 1.470 eV, a defect‐related (d,A0C) recombination process is identified at 1.411 eV for a sample temperature of 4.5 K. The defect concentration is higher near the GaAs to Si interface region and decreases with increasing GaAs layer thickness. With increasing temperature (80–300 K) the valence‐band splitting diminishes and reaches a value of 9 meV at room temperature, in good agreement with the strain values determined by x‐ray diffraction.

ISSN:0021-8979    

DOI:10.1063/1.340269

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An electrolyte for anodic oxidation of InP is described which takes into account the extreme sensitivity of its native oxide to water. It is an aqueous solution of citric acid buffered to nearly neutralpH and highly diluted by glycerine or ethylene glycol which can produce smooth native oxide films on InP. The breakdown field is about 3.5×106V/cm. Nearly no shrinkage even at temperatures up to 590 °C has been observed indicating that the oxide is very densely packed.

ISSN:0021-8979    

DOI:10.1063/1.340270

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The thermal oxidation of InP in dry oxygen has previously been shown to result in mixed oxide layers, even when grown at pressures as high as 500 atm. This appears to be caused by the slow diffusion of P and O2through the oxide relative to In. This paper reports on the oxidation of InP in steam at one and 500 atm. Growth in one atm yields an oxide with a composition very similar to those grown in dry oxygen, indicating similar growth kinetics. However, at 500 atm of steam the growth kinetics are changed dramatically and result in a uniform InPO4layer, suggesting that at high pressure, the H2O diffuses rapidly to the oxide‐InP interface where the oxidation reaction occurs.

ISSN:0021-8979    

DOI:10.1063/1.340271

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Preparation and properties of the dc reactively sputtered tungsten oxide films have been investigated in relation to the oxygen concentration in sputtering atmosphere. The films with 1500–20 700 A˚ thickness were deposited on the glass substrates maintained at 200 °C by dc reactive sputtering from a metallic tungsten target under a constant operating pressure of 6.5×10−2Torr in Ar‐1%–30% O2gas mixture. The films formed in an Ar‐3%–20% O2gas mixture are crystalline WO3, and have an electrical resistivity of 107–1011&OHgr; cm which is dependent on the oxygen concentration of the sputtering atmosphere. These films have a spectral transmittance above 80% in the visible and near‐infrared regions, and optical band gap of the films ranges from 3.15 to 2.98 eV, depending on the oxygen concentration. Densities of the film deposited in Ar‐3% O2and in Ar‐20% O2gas mixtures are 5.85 g/cm3and 6.65 g/cm3, respectively. Electrochemichromic properties of the transparent‐crystalline WO3films were studied using asymmetric cells, and were found to be dependent on the crystal orientation of the films. The films with the orientation of WO3(020) and WO3(021) formed in an Ar‐3%–6% O2gas mixture have a very good electrochromic property, and the cells composed of the crystalline WO3films have a higher coloration rate than the cells composed of the vacuum‐evaporated amorphous film. The films with the orientation of WO3(001) and WO3(021) formed in an Ar‐8%–20% O2gas mixture were found to have a poor electrochromic property.

ISSN:0021-8979    

DOI:10.1063/1.340272

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The application of a CO2laser to the controlled melting of doped silicon surfaces was studied theoretically and corroborated with previous experimental results. Because of the lack of interband transition at 10.6 &mgr;m, energy deposition was dominated by free‐carrier absorption, which could be affected by the doping concentration and the dopant spatial distribution. It was shown that for undoped samples, avalanche ionization played an important role in the initiation of the melting process. In most cases, melting could be induced on the surface without concomitant laser breakdown. The resolidified surface remained smooth under scanning electron microscopy examination. The effect of pulse duration on the controlled melting of silicon was also studied in detail. It was found that ultrashort CO2laser pulses could melt silicon without breakdown damage over a wide range of intensities and sample impurities. For nanosecond duration pulses, similar intensity ranges were not available, except for highly doped samples.

ISSN:0021-8979    

DOI:10.1063/1.340080

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Thin films of tungsten silicide with resistivities of 30–35 &mgr;&OHgr; cm have been formed by sputter depositing 710 A˚ of W metal onto (100)–oriented, 3–7 &OHgr; cm,p‐type silicon wafers. The samples were fast radiatively processed in a rapid thermal processing (RTP) system under high vacuum for time anneals ranging from 15–20 s at two temperatures (∼1100 and ∼1150 °C). The inevitable oxide barrier at the interface is shown to decrease with increasing RTP time and temperature, evidenced by both Auger electron spectroscopy and secondary ion mass spectrometry experiments. The high film stress produced by thermal considerations does not seem to effect the resulting resistivity and, furthermore, appears to relax at higher temperatures when the film surface becomes ‘‘buckled.’’

ISSN:0021-8979    

DOI:10.1063/1.340081

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The stability towards photoelectrochemical (PEC) etching in hexacyanoferrate (II) (=R) solution has been determined for a set of single‐crystalline ternary alloys in the series GaAs1−yPy(0<y<0.8), using the rotating ring‐disk electrode technique. It was found that the stability coefficientSincreases monotonicaly but nonlinearly from a low value in the GaAs end to near 1 fory=0.8. The data are consistent with a kinetic model involving competition between decomposition and hole transfer from the valence band edge toRwith a probability determined by the thermal fluctuating energy level model. The findings are of potential interest in using selective PEC etching in preparing structures in optoelectronics and multilayer heterostructures for high‐speed electronics.

ISSN:0021-8979    

DOI:10.1063/1.340082

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Bromine atom concentrations in Br2discharges were measured by Br2absorption spectroscopy. At 3.7 MHz, the dissociation of Br2increased with power, reaching a maximum of ∼40%. The aluminum etch rate was proportional to the bromine atom concentration. In the discharge, atoms etched aluminum 20 times faster than molecules. The etch product molecule appears to be reversibly physisorbed on the brominated surface with an apparent binding energy of ∼0.2 eV/molecule.

ISSN:0021-8979    

DOI:10.1063/1.340083

出版商:AIP    

年代:1988

数据来源: AIP