摘要:

Internal strain energies for quaternary III‐V compound alloys of the type AxB1−xCyD1−yhave been estimated. The strain is attributable to the difference in bond length among the constituent compounds. Results are shown in the form of contour of the energy. The energies in AlGaAsP are relatively small; the maximum value is about 4 kJ/mol, and those in AlInPSb are large; the maximum is about 50 kJ/mol. The alloys are concluded to be hardly miscible by ordinary growth methods in the domain of strain energies larger than 19 kJ/mol. The qualities of the alloys can be predicted by the internal strain‐energy charts presented in this study. The effect of movement of atoms from the virtual crystal‐lattice sites is discussed. Comparison to the enthalpy of mixing is also made.

ISSN:0021-8979    

DOI:10.1063/1.336593

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Bulk Czochralski (CZ) and vapor phase epitaxy (VPE) layers ofnGaAs have been irradiated with 1‐MeV electrons, with doses ranging from 2×1015to 1017cm−2and temperatures ranging from 240 to 330 °C. In CZ material, up to seven defects are detected. In VPE layers, five defects are observed. The variation of their introduction rates have been determined versus the temperature of irradiation. This study allows us to show that these traps are complex defects, due to the interaction of arsenic interstitial (IAs) with the impurities contained in the material. The fact that we detected the introduction of traps having the same electrical characteristics as the well‐known EL5 and EL2 traps found usually in unirradiated materials provides information on their nature. Finally, a complete compensation of the material can be obtained, which demonstrates the feasibility of producing semi‐insulating layers by irradiation.

ISSN:0021-8979    

DOI:10.1063/1.336594

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The electrical response of BaTiO3ceramics to the strong shock compression well above the Hugoniot‐elastic limit or ferroelectric‐paraelectric transition pressure is studied to separate and identify the causes of shock‐induced electrical response of ferroelectric materials. Measurements of voltage and current histories under shock compression are performed by using poled and nonpoled specimens, assemblies of both parallel and normal modes, and explosive systems. In order to consider the effects due to elastic‐plastic deformation and shock‐induced conduction, the Hugoniot compression curve and electrical conductivities are also measured by using nonpoled specimens. The Hugoniot‐elastic limit stress is determined to be 4.8–6.4 GPa for porous specimens with 1.7–4.4% porosity, and the shock velocity (Us) and particle velocity (Up) Hugoniot can be closely described asUs=4.29+1.66Upkm/s in the plastic region. The electrical conductivity values at 12‐ and 29‐GPa peak stresses are measured to be 2.1×10−3and 4.8×10−2S/cm, respectively. Both voltage histories for the parallel and normal modes at 12‐ and 29‐GPa peak stresses show similarly increasing signals with time. Although the signals of the 29‐GPa peak stress show large internal losses due to shock‐induced conduction, these signals are reasonably analyzed by a simple analytical model based on the ferroelectric‐paraelectric transition. The relative dielectric constant values under shock compression calculated by the model from the measured voltage histories are in the range (5–71)×103, which is consistent with those measured under static compression. Current histories for the parallel and normal modes at the 12‐GPa peak stress show a pulse‐shaped signal and a constant‐current‐shaped signal, respectively, whose total integrated charges are in agreement with those due to the initial remanent polarization, with the losses less than 20%. It is concluded that the measured electrical responses of poled BaTiO3ceramics to the shock compression well above the Hugoniot‐elastic limit are caused not by piezoelectricity, but chiefly by the shock‐induced ferroelectric‐paraelectric transition, in this study.

ISSN:0021-8979    

DOI:10.1063/1.336595

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Alternating layers of high‐ and low‐resistivity silver thiogallate (AgGaS2) were grown sequentially by liquid‐phase epitaxy on AgGaS2substrates using the vertical dipping technique. High‐resistivity layers were grown by using KCl‐AgGaS2solutions while low‐resistivity layers were grown from Ge‐AgGaS2‐KCl solutions. Layer growth of such a multilayer device and demonstration of its electro‐optic response for filter application are described.

ISSN:0021-8979    

DOI:10.1063/1.336596

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Liquid‐phase‐epitaxial (LPE) growth of AlGaAs layers has been used in fabricating InGaAsP buried heterostructure visible lasers on GaAs substrate. InGaAsP/InGaAsP double heterostructure wafers were grown on thep‐type GaAs substrates by means of the melt‐back method prior to the LPE growth for eliminating phosphorus contamination. An SiO2film mask was deposited on the epitaxial wafer surface by the rf sputtering, and photoetched with stripes of 7–10 &mgr;m width in the ⟨110⟩ direction. After etching to the firstp‐InGaAsP cladding layer with a 3% Br‐methanol solution, the second LPE growth ofn‐AlGaAs andp‐GaAs layers was carried out. The InGaAsP active region is entirely surrounded by the InGaAsP cladding layers and the AlGaAs burying layer, therefore, it becomes possible to provide both lateral and vertical carrier and optical confinements.I‐Lcharacteristics were measured at room temperature under pulsed operation, but the lasing action was not obtained. The peak wavelength of the electroluminescence was 785 nm. The transverse mode behavior was analyzed by means of the effective refractive index approximation. And it seemed that this buried heterostructure is suitable for the transverse mode control of InGaAsP visible laser diodes.

ISSN:0021-8979    

DOI:10.1063/1.337034

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The sintering of sputter‐produced, silica‐supported platinum thin films was studied using electron microscopy and x‐ray diffraction following treatments in both reactive (ethylene oxidation—O2+C2H4) and nonreactive atmospheres (vacuum, O2, N2, C2H4, CO2, H2O). Sintering behavior in nonreactive atmospheres (thermal sintering) was found to be insensitive to the gas phase and was a function of temperature only. Changes in film structure following thermal sintering were not dramatic and were readily explained by conventional models. In contrast, sintering in reactive atmospheres was found to be a strong function of temperature and the O2/C2H4ratio. Over a relatively narrow temperature range (770–970 K), the surface was found to be dramatically restructured with plantinum completely stripped from some areas and large particles forming in others. This type of sintering (reaction‐enhanced sintering) possibly results from the interaction of homogeneously formed radicals with the metal surface to form metastable mobile intermediates.

ISSN:0021-8979    

DOI:10.1063/1.336597

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The stimulated emission spectra of photoexcited AlxGa1−xAs, 0.42≤x≤0.46 (near the direct‐indirect gap crossoverxc=0.435) were measured at low temperatures as a function of the illuminated stripe length and excitation intensity. Based on these data, the gain spectra and gain saturation behavior were obtained. The observed gain spectra are explained by calculating the radiative recombination of an electron‐hole plasma of constant density with fair agreement between theory and experiment. It is found that abovexcthe gain spectrum is due to electrons in the indirect‐gap minima (X) whose wave function is strongly admixed with the (&Ggr;) minimum by alloy disorder. The saturation of the stimulated emission at higher excitation intensity and at larger stripe length could be explained qualitatively for the direct‐gap samples by a model based on electron and hole relaxation within their respective Fermi seas. This model yields the stimulated emission shift towards lower energy with increased excitation intensity or stripe length. The behavior of the indirect‐gap samples is different: both ends of the gain spectrum saturate. This behavior cannot be explained by the proposed model.

ISSN:0021-8979    

DOI:10.1063/1.336598

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The photothermal deflection technique has been extended as a contactless,insitumethod to investigate transport in solids with an emphasis on semiconductors. A theoretical model is developed which quantitatively describes the transport behavior, and is shown to be in excellent agreement with experimental results. For semiconductors, this approach yields the thermal diffusivity, the electronic diffusivity, the minority‐carrier lifetime and the surface recombination velocity.

ISSN:0021-8979    

DOI:10.1063/1.336599

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new technique is described in which a transient thermoelectric (TTE) voltage of a semiconductor is measured after a pulsed laser irradiation—a modification of photodiffusion or Dember effect. This technique has been successfully applied to test samples ofn‐ andp‐Si over the wide time range from 20 ns to 2 s and the temperature 120–284 K. The decay curves of the TTE voltage consist of three stages with the characteristic relaxation or decay times. Stage 1 with the relaxation time &tgr;1, is associated with the carrier generation and recombination and explained by the Dember effect. Stage 2 characterized by the relaxation time &tgr;2, is due to the diffusion of majority carriers from a higher to a lower temperature region; forp‐Si, a double‐relaxation process is observed arising from the difference in the drift mobilities of light and heavy holes. At stage 3, the TTE voltage vanishes completely, which can be reasonably interpreted by the diffusion of thermal flux or phonons along a temperature gradient produced by the laser pulse. Analytical expressions for each stage are presented to discuss these experimental results.

ISSN:0021-8979    

DOI:10.1063/1.336600

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We describe a new technique to determine the density of localized states in the energy gap of amorphous silicon alloys from the temperature dependence of the low field conductance ofn‐i‐ndiodes. This new technique allows us to determine the bulk density of states in the center of a device. It involves fewer assumptions than other established techniques, and by varying the intrinsic layer thickness the density of states within approximately 400 meV of midgap can be determined. We measured the temperature dependence of the low field conductance of amorphous silicon alloyn‐i‐ndiodes with intrinsic layer thicknesses of 0.55, 0.45, and 0.15 &mgr;m and deduced the density of localized states to be approximately 5×1016cm−3 eV−1at 0.45 eV and 5×1017cm−3 eV−1at 0.24 eV below the bottom of the conduction band.

ISSN:0021-8979    

DOI:10.1063/1.336601

出版商:AIP    

年代:1986

数据来源: AIP