摘要:

Single‐ and multiple‐energy Be, S, Si, and Ne ion implantations were performed at room temperature in InSb grown on semi‐insulating GaAs substrates. The implanted material was subjected to both isochronal and isothermal annealing schemes. The as‐implanted and annealed material was characterized by Hall, secondary ion mass spectrometry, and x‐ray rocking curve measurements. The as‐implanted material is highlyn‐type for all implant species used in this study. A maximump‐type activation of 90% andn‐type activation of 16% was achieved for Be and S implants, respectively. Be activation depends on the thickness of the InSb layer. No in‐diffusion of Be and S was observed even after 500 °C anneal. The Si implant has an amphoteric doping behavior.

ISSN:0021-8979    

DOI:10.1063/1.348394

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Microinhomogeneities in semi‐insulating, liquid‐encapsulated Czochralski (LEC) GaAs crystals were investigated by selective photoetching and spatially resolved photoluminescence at 1.8 K. The interaction of point defects with dislocations was studied by annealing the samples in a metalorganic chemical vapor deposition reactor under AsH3pressure. The changes in microstructure, induced by the anneal process, were investigated for both undoped and Cr‐doped crystals. A weakening of the photoetching contrast after annealing was observed for both types of crystals, with no essential difference between undoped and Cr‐doped ones. The overall near‐band‐gap photoluminescence (PL) intensities were found to have increased after annealing. This increase amounted to about one order of magnitude for the Cr‐doped crystals, and two orders of magnitude for the undoped ones. In addition, for the undoped samples the contrast in PL intensity between dislocated areas and the undisturbed crystal matrix was increased by the anneal process. Analysis of the local PL spectra taken at different regions on these samples showed a strong enhancement of acceptor‐bound exciton (A0,X) transitions relative to donor‐bound exciton (D0,X) transitions, especially at dislocated areas. Furthermore, a new emission for LEC GaAs at 1.5116±0.0003 eV was also found to be strongly enhanced at these regions. The PL results are explained by the disappearance of deep, nonradiative, excess As‐related PL killer centers during annealing. The disappearance is proposed to proceed via diffusion of interstitial As atoms and the formation of As precipitates, for which dislocations act as nucleation centers. Additional deep level photoluminescence spectra of the 0.65 and 0.80‐eV emission bands are shown to be in accordance with the proposed model.

ISSN:0021-8979    

DOI:10.1063/1.348395

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Semitransparent palladium contacts on mercuric iodide were studied by low temperature photoluminescence spectroscopy and thermally stimulated conductivity. These contacts were deposited either by thermal evaporation or by plasma sputtering. Changes due to palladium deposition were found in the photoluminescence spectra and were attributed to modifications in the stoichiometry within the palladium/mercuric iodide interfacial region. Thermally stimulated conductivity measurements revealed two dominant traps with activation energies of 0.010 and 0.54 eV. The importance of these traps in the application of nuclear detection is discussed.

ISSN:0021-8979    

DOI:10.1063/1.348396

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The effect of reduced growth area on the misfit accommodations of InxGa1−xAs/GaAs grown by molecular beam epitaxy has been studied with cross‐sectional transmission electron microscopy (XTEM). Composition grading techniques as well as strained‐layer superlattices were used for InxGa1−xAs compositions up tox=0.53 and growth areas which ranged from approximately 10 cm2(blanket areas) to 4 &mgr;m2squares. Results indicate that the use of step‐composition grading and linear‐composition grading are particularly effective when combined with reduced growth areas up to 30×30 &mgr;m and InxGa1−xAs compositions up tox=0.25. Dislocations which are generated for misfit accommodation during growth are effectively driven to the edges of the patterned growth areas with considerably fewer interactions than dislocations nucleated in blanket areas. XTEM samples prepared from blanket areas were generally found to contain randomly distributed threading dislocation‐free regions on the order of 20–30 &mgr;m in width bounded by high density dislocation pile‐ups. Higher InxGa1−xAs compositions resulted in large densities of threading dislocations with Burgers vectors perpendicular to the growth direction, particularly for step‐composition graded layers. We attribute this behavior to roughening of the growth interface.

ISSN:0021-8979    

DOI:10.1063/1.348397

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

CuPt type ordering, which consists of a monolayer compositional modulation along one of the 4 ⟨111⟩ directions in the lattice, was studied using transmission electron microscopy for GaAs1−xPxwith values ofxextending from 0.25 to 0.85. The samples were grown by organometallic vapor phase epitaxy on nominal (001) GaAs substrates that were misoriented by varying amounts in three directions. No CuPt type ordering was observed for GaAs1−xPxwithx≤0.35, while ordering was found to occur for 0.4≤x≤0.85. The direction of substrate misorientation has a major effect on the determination of which of the four possible CuPt variants are formed for 0.4≤x≤0.85. Two variants, with ordering on the (1¯11) and (11¯1) planes, appear for epilayers grown on substrates oriented exactly on the (001) plane and for substrates misoriented by 6° towards the [110] direction. Only one variant, with ordering on the (1¯11) plane, appears for epilayers grown on substrates misoriented by 6° towards [1¯10]. These ordering‐induced spots observed in transmission electron diffraction (TED) patterns for GaAsP occur only for the [110] cross section. From TED studies of GaInP grown on similar substrates, we conclude that the CuPt variants in GaAsP are exactly the same as for GaInP. Further evidence supporting this conclusion was obtained by growing first a layer of GaInP followed by a layer of GaAsP. High‐resolution dark field electron micrographs show domains of the same variants in both layers. A mechanism describing the formation of the specific ordered variant for both GaAsP and GaInP is proposed. From studies of ordering in a strain‐layer superlattice, the strain due to lattice mismatch was found to play no significant role in the propagation of ordered domains. Microtwins, also generated due to lattice mismatch, can act as domain boundaries and prevent the propagation of the ordered domains.

ISSN:0021-8979    

DOI:10.1063/1.348398

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Roughness and general surface topography of polished Si wafers were systematically studied on an angstrom to nanometer scale by scanning tunneling microscopy (STM). Evaluation of a large number of STM images by using a simple classification scheme assures statistically relevant results without the disadvantages and loss of information connected with averaging the rms roughness or similar methods. For the flat parts of the surface, a rms roughness of 1.2–1.8 A˚ is found, comparable to that derived from light scattering and diffraction measurements on similar surfaces. Significant amounts of the surfaces were found to exhibit more pronounced structures, contrasting results of other techniques. The reliability and applicability of STM measurements on technical surfaces, on an angstrom to nanometer scale, is discussed in the light of these results.

ISSN:0021-8979    

DOI:10.1063/1.348399

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Epitaxial growth of CoSi2on (111)Si inside two‐dimensional and linear oxide openings by rapid thermal annealing has been investigated by transmission electron microscopy. Both annealing temperature and time were found to be critical in obtaining 100% epitaxy. The size of oxide openings and annealing temperature were found to exert strong influences on the morphology of epitaxial CoSi2on silicon. The faceting of CoSi2was found to occur at a lower temperature inside oxide openings of smaller size. The change in morphology of epitaxial CoSi2with the size of oxide openings in the present study indicated that interfacial energy and/or stress, in addition to the surface energy, are important in determining the morphology of epitaxial CoSi2on (111)Si.

ISSN:0021-8979    

DOI:10.1063/1.348400

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this paper, we report the growth of epitaxial films of ZnGeP2on GaP and Si substrates of (001) and (111) orientations by open tube organometallic chemical vapor deposition. Generally, smaller growth rates are required to achieve similar film quality on (111) GaP as compared to growth on (001). For the growth on (001) GaP thec‐axis strain determined by x‐ray diffraction agrees with the expected strain for a lattice mismatch of 0.0026 between thea‐axis lattice parameters of ZnGeP2and GaP. Based on the continuous increase of thec‐axis lattice parameters and the gradual weakening of the chalcopyrite structure superlattice reflections, a continuous transition is proposed from the ordered structure of ZnGeP2towards diamond structure of Ge via partially disordered metastable solid solution of ZnGeP2‐Ge. Cross‐sectional transmission electron microscopy reveals twinning of epitaxial ZnGeP2‐Ge films on (111) GaP. The twinning density is related to both the growth rate and the flow rate ratio of Zn(CH3)2to GeH4at constant flow rate of PH3and H2. Twins are also formed in ZnGeP2growth on Si substrates.

ISSN:0021-8979    

DOI:10.1063/1.348401

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The conditions and reaction mechanism of W/Ni/Si80Ge20hot‐press bonding have been studied. It was found that a Ni/Si80Ge20bond can be formed using low pressure, 19.6 MPa, in the temperature range between 780 and 900 °C in a short time. The kinetics follows a parabolic pattern, suggesting it is a diffusion‐controlled process. The activation energy is 2.7 eV and the parabolic rate constant is given byKP= 4.0 × 1014 exp(−3.2×104/T) (&mgr;m2/min). The bonding interface has a multilayered structure. A phenomenological mechanism of the bonding formation has been proposed based on scanning electron microscopy observations and energy dispersive spectroscopy. The cracking problem due to thermal stress is discussed based on Oxx’s equation. It was found that bonds free from cracks in the Si80Ge20alloy are formed when the Ni consumption (as measured by the thickness of the nickel layer) is sufficiently small (<40–45 &mgr;m) and the post‐hot‐press cooling is slow. On the other hand, tungsten and nickel react during hot pressing at higher temperature, forming WNi4. As an interlayer, nickel can join the tungsten sheet and the Si80Ge20together. It has been also demonstrated that a thin nickel layer formed by vapor deposition on a tungsten sheet may be used as the interlayer in place of nickel sheet.

ISSN:0021-8979    

DOI:10.1063/1.348402

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this work we have applied the admittance spectroscopy technique to characterize the DX centers in AlxGa1−xAs alloys doped with silicon. Our experimental results reveal the existence of two DX centers related to silicon in AlxGa1−xAs alloys, named DX‐I and DX‐II centers, with thermal activation energies of 0.370 and 0.415 eV, respectively. These values are lower than those obtained by other authors using capacitance techniques. To explain this disagreement it should be noticed that capacitance techniques can be affected by the nonexponential behavior of the thermal emission transients of the DX centers in AlxGa1−xAs alloys.

ISSN:0021-8979    

DOI:10.1063/1.348403

出版商:AIP    

年代:1991

数据来源: AIP