摘要:

The accommodation of lattice mismatching in InPAs layers with thickness from one monolayer to 200 A˚ grown on InP substrates is measured by extended x‐ray‐absorption fine structure. Measured critical thicknesses agree with model calculations. In the layers beyond the critical thickness, gradual lattice accommodation with increase of the layer thickness is observed. The lattice accommodation mechanism beyond the critical thickness is discussed by comparison with the calculations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359381

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A combined ion‐beam and molecular‐beam‐epitaxy (CIBMBE) system has been developed. This system consists of an ion implanter capable of producing ions in the energy range of 30 eV–30 keV and conventional solid‐source MBE. As a successful application of CIBMBE, low‐energy (100 eV) carbon ion (C+) irradiation during MBE growth of GaAs was carried out at substrate temperaturesTgbetween 500 and 590 °C. C+‐doped layers were characterized by low‐temperature (2 K) photoluminescence (PL), Raman scattering, and van der Pauw measurements. PL spectra of undoped GaAs grown by CIBMBE revealed that unintentional impurity incorporation into the epilayer is extremely small and precise doping effects are observable. CAsacceptor‐related emissions such as ‘‘g,’’ [g‐g], and [g‐g]&bgr;are observed and their spectra are significantly changed with increasing C+beam current densityIc. PL measurements showed that C atoms were efficiently incorporated during MBE growth by CIBMBE and were optically well activated as an acceptor in the as‐grown condition even forTgas low as 500 °C. Raman measurement showed negligible lattice damage of the epilayer bombarded with 100 eV C+with no subsequent heat treatment. These results indicate that contamination‐ and damage‐free impurity doping without postgrowth annealing can be achieved by the CIBMBE method. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359361

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The formation chemistry and growth dynamics of thin‐film CuInSe2grown by physical vapor deposition have been considered along the reaction path leading from the CuxSe:CuInSe2two‐phase region to single‐phase CuInSe2. The (Cu2Se)&bgr;(CuInSe2)1−&bgr;(0<&bgr;≤1) mixed‐phase precursor is created in a manner consistent with a liquid‐phase assisted growth process. At substrate temperatures above 500 °C and in the presence of excess Se, the film structure is columnar through the film thickness with column diameters in the range of 2.0–5.0 &mgr;m. Films deposited on glass are described as highly oriented with nearly exclusive (112) crystalline orientation. CuInSe2:CuxSe phase separation is identified and occurs primarily normal to the substrate plane at free surfaces. Single‐phase CuInSe2is created by the conversion of the CuxSe into CuInSe2upon exposure to In and Se activity. Noninterrupted columnar growth continues at substrate temperatures above 500 °C. The addition of In in excess of that required for conversion produces an In‐rich near‐surface region with a CuIn3Se5surface chemistry. A model is developed that describes the growth process. The model provides a vision for the production of thin‐film CuInSe2in industrial scale systems. Photovoltaic devices incorporating Ga with total‐area efficiencies of 14.4%–16.4% have been produced by this process and variations on this process. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359362

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect of a plasma‐surface interaction on the adhesion force of a thin metal film was investigated using a bilayer system consisting of a TeSeF film and a fluorocarbon subbing layer. The change in an ablative hole opening process with a focused laser beam in this bilayer system was also affected by the modification of the adhesion force due to the plasma‐surface interaction. An Ar plasma treatment of the fluorocarbon subbing layers prior to the TeSeF film deposition increased the adhesion force and the threshold energy for the ablative hole opening. Even without such intentional plasma treatment, the interface chemical structure depended on the plasma‐surface interaction during the TeSeF active layer deposition, where the active layer was deposited by the rf or dc reactive sputtering of TeSe in a SeF6/Ar gaseous mixture. The rf sputtered TeSeF film required larger threshold energy for hole opening than the dc sputtered one. The modified interface chemical structure by the plasma‐surface interaction was analyzed using x‐ray photoelectron spectroscopy. The increase in the threshold energy for hole opening for the plasma‐treated subbing layer and for the rf sputtered TeSeF film was due to the increase in the cross‐linking density in the fluorocarbon polymer, unsaturated bonds, and dangling bonds at the interface in the bilayer system. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359555

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Mo/Si and W/C multilayer films were fabricated by magnetron sputtering. Cross‐section transmission electron microscopy shows that these multilayers have a well‐formed layer structure. The modulation wavelength of the multilayer can be precisely determined from the spacing of the satellites in the low‐angle regions of both electron and x‐ray‐diffraction patterns. Experimental results show that the refraction corrections to the Bragg condition for electron and x‐ray diffractions are in opposite directions. The physical significance of the difference between the two corrections is discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359363

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have determined the alloy composition of modulation doped AlxGa1−xAs/GaAs heterostructure by Raman scattering and photoreflectance spectroscopy at room temperature. We also demonstrated that Franz‐Keldysh oscillations in photoreflectance spectroscopy can be used to evaluate the band gap of semiconductor heterostructure. The band gap measured by Franz‐Keldysh oscillations of photoreflectance spectrum is 1.865 eV. The alloy composition calculated from the band gap is 0.30. From the frequency positions of ‘‘GaAs‐like’’ and ‘‘AlAs‐like’’ phonon modes of the Raman scattering data, the value of the alloy composition was evaluated to be 0.29 which is in good agreement with the photoreflectance result. Both values also agree with the target composition in the molecular beam epitaxy growth and the target composition is equal to 0.30. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359364

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The microscopic nature of the degradation of oxide layers in Si/SiO2/Si structures induced by annealing in the temperature range 1200–1320 °C in inert or weakly oxidizing atmospheres has been studied. Electron‐spin‐resonance measurements have been performed on unannealed and annealed samples subsequently subjected to &ggr; orXradiation or hole injection. Two oxygen‐vacancy‐related defect centers were observed, the monovacancyE&ggr;’center and the multiple vacancyE&dgr;’—both were observed in substantially larger numbers in annealed oxides as compared to unannealed oxides. Etchback profiling of the paramagnetic defect distributions shows that they are distributed nonuniformly throughout the annealed oxides with the highest densities close to the two Si/SiO2interfaces. Electrical measurements of fixed oxide charge induced byXirradiation indicate that annealing results in the creation of both positive and negative charge traps. The numbers of positive trapped charges and their radiation dose dependence are inconsistent with their origin being identified simply with the paramagnetic oxygen‐vacancy centers. Infrared measurements of the O interstitial content of the float‐zone Si substrates of annealed and unannealed samples reveal that the interstitial concentration increases as a function of anneal temperature/time. Atomic force microscopy measurements reveal that the SiO2/Si substrate interfaces are roughened during high‐temperature annealing. The data are interpreted in terms of a model in which oxygen is gettered from the oxide film into the over‐ and underlying Si. The O are incorporated into the Si as interstitials and it is their solubility limit at the anneal temperature which drives the gettering process. The oxygen‐vacancy defect profiles near to both Si/SiO2interfaces are not well predicted by the gettering model suggesting that other interface‐related defect creation processes may be active. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359365

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated laterally alignedpnjunctions formed by a one‐step molecular beam epitaxial growth of Si‐doped GaAs and AlGaAs on patterned substrates. Current‐voltage (I‐V) and cross‐sectional electron beam induced current measurements suggested that the junctions’ configuration was rathernn−pnwith a highly compensatedn−region than simplenpnconfiguration. Temperature dependence of theI‐Vcurves was also examined and the breakdown mechanism was found to be avalanche multiplication. Transmission electron microscope measurement revealed that the critical angle of crystal plane which determines the conduction type of Si‐doped GaAs is exactly 25°, i.e., the (311)Aplane. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359367

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Gallium nitride is grown by metalorganic vapor phase epitaxy with and without a low‐temperature‐grown AlN buffer layer. Variations in the surface morphology and the layer properties are compared between two‐step growth and direct growth to study the effects of various growth conditions. It is found that (i) conditions that stabilize the GaN(0001) surface serve as guidelines for obtaining mirrored surfaces, and (ii) raising GaN growth temperature improves crystallographic, electrical, and luminescence properties of GaN. The observed improvement in the layer properties with increase in GaN growth temperature suggests that increasing N2dissociation pressure does not affect GaN properties. GaN growth conditions are analyzed thermodynamically to show that NH3in the growth ambients has the potential to suppress thermal dissociation of GaN. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359368

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate a novel method for the growth of abrupt InGaAs(P)/In(GaAs)P heterojunctions by gas source molecular beam epitaxy. We find that exposure of freshly grown InP to an As flux during growth interruption between layers of different compositions results in the substitution of surface P atoms and As atoms, thereby generating a strained transition layer at each interface. By assuring a group‐III stabilized surface during interruption required to grow InGaAs(P)/In(GaAs)P heterointerfaces, As/P substitution can be avoided, thereby resulting in improved interface quality. Heterointerface abruptness was examined by double‐crystal x‐ray diffraction and low temperature photoluminescence. The results show that the interfaces grown with the modified switching sequence are considerably more abrupt than those obtained using conventional sequences where As/P interdiffusion extends over several monolayers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359370

出版商:AIP    

年代:1995

数据来源: AIP