摘要:

High temperature stability of platinum silicide, formed by reacting metal with silicon or by cosputtering metal and silicon in a desired ratio, has been studied. The properties of films, thus formed, were examined as a function of annealing temperature using a resistance measuring technique, Rutherford backscattering, Auger and x‐ray analyses, transmission and scanning electron microscopic techniques, and by measuring forward current‐voltge (I‐V) characteristics of the siliciden‐silicon Schottky diodes. It is shown that cosputtering silicon rich alloys prevents agglomeration of the silicide, but increases the resistivity and decreases the Schottky barrier height of the film. Platinum silicide dissolves increasing amounts of silicon on high temperature (700–1000 °C) treatments causing considerable degradation of properties. Although cosputtering silicon rich alloys reduces this behavior, electrical properties such as forwardI‐Vcharacteristics still degrade due to high temperature anneals.

ISSN:0021-8979    

DOI:10.1063/1.332010

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The interface structures resulting from the alloying reactions between a Au/Ni/Au‐Ge composite film and a (100) GaAs substrate were studied by transmission electron microscopy and scanning transmission electron microscopy. Electron microscope examinations of the cross‐sectional samples prepared in this study offered excellent lateral and depth resolution of local structures which are not available by other analytical techniques used previously in similar studies. The distributions and chemical compositions of various phases formed, and the morphologies of the interfaces between these phases were monitored and compared with the measured contact resistances at three different stages of alloying. A correlation between the interface structure and the contact resistance was found.

ISSN:0021-8979    

DOI:10.1063/1.332011

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The room temperature pulsed operation of In0.49Ga0.31Al0.20P/In0.49Ga0.51−xAlxP/In0.49Ga0.31Al0.20P(x=0.00–0.03) double heterostructure (DH) laser diodes have been achieved for the first time. The lasing wavelength was 0.66–0.68 &mgr;m with a threshold current density of 2.6–3.6×104A/cm2at 26 °C. These results were achieved by growing DH wafers by molecular beam epitaxy (MBE). Key points in the successful MBE growth of these DH wafers were, first, the realization of low resistancep‐type andn‐type InGaAlP layers by reducing contamination in the growth chamber. This was done by installing a substrate loading room with an interlock valve and a substrate transfer mechanism. The second was the realization of an abruptp‐njunction by the use of Si instead of Sn as ann‐type dopant.

ISSN:0021-8979    

DOI:10.1063/1.332012

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The influence of excitation density and excitation energy on the low‐temperature photoluminescence spectra of GaAs doping superlattices has been studied in detail. In addition to the strongly tunable luminescence across the indirect gap in real space, which is the specific recombination process in doping superlattices, luminescence lines near the band gap of bulk GaAs, originating from vertical electron‐hole recombination processes, are observed. The relative intensities of these vertical luminescence transitions increase at excitation energies close to the bulk band gap and also at high excitation densities. We explain this increase by a simple model based on the classical evaluation of the relaxation kinetics of photoexcited carriers in momentum and real space. The significant result of our investigation is the observation that the luminescence efficiency in GaAs doping superlattices remains constant if the excitation density is varied. Consequently, the relative weight of nonradiative recombination processes isnotincreasing if the recombination lifetimes are enhanced by several orders of magnitude by lowering the value of the effective gap.

ISSN:0021-8979    

DOI:10.1063/1.332013

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Epitaxial layers ofp‐type In1−x−yGaxAlyAs doped with Mn were grown by molecular beam epitaxy. The doping characteristics and electrical properties are studied using Hall measurements in the temperature range between 100 and 300 K. Secondary ion mass spectrometry (SIMS) was used to study Mn profiles and diffusion coefficients. The maximum hole concentration attainable at room temperature is relatively independent of the As flux and is found to decrease from 4×1018fory=0 to 2×1016cm−3fory=0.48. The experimental results of the resistivity and Hall effect are used to determine the densitiesNa, Ndof acceptors and compensating donors and the activation energy. The acceptor activation energyEaincreases from 50 aty=0 to 200 meV aty=0.23.Eais found to be independent of the hole concentration and the arsenic flux used during the molecular beam epitaxial growth. The hole mobility for hole concentration of ∼1017cm−3is about 140 cm2 V−1 s−1and decreases with increasingy. SIMS measurements of the Mn profiles show that Mn diffusion is significant at temperatures 650 °C and above, but is insignificant under the growth condition at 493 °C. Abrupt junction and sharp Mn pulses (<0.15 &mgr;m wide) have been obtained. Mn surface segregation is negligible at growth temperatures above 500 °C.

ISSN:0021-8979    

DOI:10.1063/1.332014

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We report on the growth by molecular beam epitaxy of high‐quality GaAs and AlxGa1−xAs (x≲0.43), and discuss the effect of system parameters on material quality. The highest Hall mobility in GaAs at 77 °K was 144 000 cm2/V sec, and the photoluminescence spectra of undoped layers exhibited a strong free exciton line and a much reduced carbon peak with no carbon‐related defects. A slow growth process at a substrate temperature of 600 °C produced excellent AlxGa1−xAs whose luminescence spectrum showed a distinct excition peak 4 meV wide. This AlxGa1−xAs is compared to layers grown at a faster rate at substrate temperatures of 700 °C.

ISSN:0021-8979    

DOI:10.1063/1.332015

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We present a calculation of the dielectric function for a quasi‐two‐dimensional electron gas (Q2D) and compare our results with those obtained for two‐dimensional (2D) and three‐dimensional (3D) electron gases. We also compare our results to those obtained using the Thomas–Fermi approximation. We find that for a Q2D system with an active layer of thickness 100 A˚, the use of the 2D and Thomas–Fermi approximations overestimate the dielectric function and the amount of screening except for small wave vector disturbances. We also compare our approach to that of Stern and Howard [Phys. Rev.163, 816 (1967)] and find that the approaches agree if we make the Thomas–Fermi approximation. When we apply our results to the problem of the calculation of the momentum relaxation rate from a screened Coulomb potential due to scattering from ionized impurities, we find that our approach leads to a larger scattering rate than that using the Thomas–Fermi approximation because of the latter’s overestimate of the effect of screening.

ISSN:0021-8979    

DOI:10.1063/1.332016

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We calculate the mobility of carriers in a quantum well structure when they are scattered by ionized impurities in the size‐quantum limit (SQL) where the carriers are assumed to populate only the lowest quantized energy level. It is found that the probability of scattering due to ionized impurities decreases with the well thickness in contrast to the case of acoustic phonon scattering where the scattering probability is enhanced under the conditions of the SQL. The temperature and thickness dependence of the mobility depends critically on the screening of the Coulomb potential due to the presence of the ionized impurities.

ISSN:0021-8979    

DOI:10.1063/1.331963

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Raman instability of the Stoke’s component of the scattered electromagnetic wave has been investigated analytically in ann‐type nondegenerate piezoelectric semiconductor plasma subjected to a large longitudinal magnetostatic field. The general dispersion relation has been obtained following the coupled mode theory and considering that the scattering is due to both the molecular vibrations produced due to the pump wave at a frequency equal to that of the transverse optical phonons and the electron plasma wave. The dispersion relation has been solved for both cases of scattered electromagnetic waves (i.e., in the cases of left‐hand and right‐hand circularly polarized waves). The threshold value of the pump amplitude necessary for the onset of instability and the growth rate of the unstable mode well above the threshold have been obtained analytically for both the modes. The relevant experiment has not been reported. It is observed that with the increase in the longitudinal magnetostatic field, the threshold value of the pump amplitude increases while the growth rate decreases in both cases. Numerical estimates have been made forn‐type InSb at 77 K irradiated with a pulsed 10.6‐&mgr;m CO2laser to obtain the necessary electric field. The analytical as well as numerical results have been compared with those of Ghosh [J. Appl. Phys.52, 4667 (1981)] while studying the Brillouin instability in longitudianally magnetizedn‐type semiconductors.

ISSN:0021-8979    

DOI:10.1063/1.331964

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Composite materials exist, which are composed of elongated conductors and granular insulators. For the effective conductivity of such materials, the ordinary effective medium theory and the random resistor network models cannot be efficiently applied. As an approach to the problem, we compute by the finite element method the effective conductivity of triangular, square, and hexagonal channeling textures, composed of continuous conductive channels and islands of insulators. As shown by the results, the effective conductivities of the three patterns are nearly equal when the channel widths of the textures are the same. And compared with a granular conductor‐insulator composite material, the three textures have a very conductive geometrical configuration, because neither island nor dead end conducting regions exist in the three patterns. If we accumulate such data for the effective conductivity of materials with a definite composite structure, we can predict the outline of the geometrical configuration of a composite material or inhomogeneous medium by measurement of the conductivity and volume components.

ISSN:0021-8979    

DOI:10.1063/1.331965

出版商:AIP    

年代:1983

数据来源: AIP