摘要:

Data are presented on a photopumped rectangular (w=40 &mgr;m,l=250 &mgr;m) quantum well heterostructure (QWH), with variable resonatorQalong the sample, showing that phonon‐assisted laser operation predominates. To achieve variable resonatorQ, the QWH sample is heat sunk embedded in In over half of its length (reflecting edges, highQ), as opposed to simple contact with a Au shim over the remaining half and no reflecting metal on the sample edges (lowQ). Photopumping at the lowQ, highQboundary near the sample center turns on and off then=1 confined‐particle recombination transition (E11) and sets a higher energy experimental (as well as calculated) reference, ℏ&ohgr;2=E11, for the lower energy phonon‐assisted laser operation, ℏ&ohgr;1=E11−ℏ&ohgr;LO.

ISSN:0003-6951    

DOI:10.1063/1.102646

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Acceleration of thermal donor formation at 400 °C in Czochralski Si by a hydrogen plasma has been observed using low‐temperature infrared absorption and spreading resistance probe measurements. The accelerated formation in as‐grown Si is attributed to hydrogen diffusion and catalyzed conversion of electrically inactive nuclei to thermal donors. When the nuclei concentration is small such as in rapid thermal annealed Si, hydrogen interaction at SiO bonds is suggested as the rate‐limiting step in thermal donor formation.

ISSN:0003-6951    

DOI:10.1063/1.102652

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The experimental results of the rapid thermal oxidation in the initial oxidation regime of molecular beam epitaxy grown GeSi strained layers are reported. It is shown that the dry oxidation rate of GeSi is the same as that of Si at different temperatures. After a very short initial time (∼10 s), the oxide thickness appears to be a linear function of time, which suggests that the kinetics of oxide growth during dry oxidation is limited by surface reaction controlled mechanisms. Further, the oxidation rate in the thin oxide regime is not affected by the Ge content up to 20% in the GeSi strained layer for dry oxidation. Using secondary‐ion mass spectrometry, it is found that Ge is completely rejected out of the SiO2layer which is formed during oxidation, and a Ge‐rich layer is formed at the SiO2/GeSi interface. A significant amount of Ge is found to diffuse into the underlying GeSi layer during the growth of thin oxide films.

ISSN:0003-6951    

DOI:10.1063/1.102653

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Various models have been developed to address the problem of ‘‘Fermi level pinning,’’ i.e., why the barrier height varies much less than the Schottky metal work function limit. The most widely accepted mechanism is some variant of the metal‐induced gap state model. However, recent experimental data on (100)InxGa1−xAs surfaces and interfaces (0≤x≤1) suggest that the surface or interface Fermi level can assume values which lie well outside the variance associated with Fermi level pinning; in fact, recent data suggest the achievement of the Schottky limit. Furthermore, studies of epitaxially grown layers where dopant incorporation is dependent on an interface Fermi level suggest that such Fermi level positions are not always pinned. In order to account for these recent results, along with the pinned values, we introduce the concept of an insulating layer like surface reconstruction. Recent calculations suggest that reconstructions of the GaAs(100) surface are insulating. Thus, we suggest that the GaAs(100) metal interface is often a metal (M)/surface reconstruction layer (I)/GaAs bulk (S), or MIS‐like. This approach attempts to reconcile disparate models of interface behavior by showing the limits of validity of these models with respect to the actual physical structure of the interface in question.

ISSN:0003-6951    

DOI:10.1063/1.102654

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have grown InGaAs/InAlAs quantum wells and InGaAs, InAlAs single layers over InP nonplanar substrates. Photoluminescence, transmission electron microscopy, and energy‐dispersive x‐ray analysis give evidence for large lateral thickness and compositional variations, which lead toinsitumodification of the growth profile. These effects, which differ for InGaAs and InAlAs, reveal the importance of surface migration in (Al,Ga)InAs. Our results demonstrate a tool forinsitulateral patterning of this material system.

ISSN:0003-6951    

DOI:10.1063/1.102655

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is well known that carrier depth profiles obtained by the capacitance‐voltage (C‐V) measurement method provide carrier information only beyond the initial semiconductor depletion region. A novel new method has been developed within the depletion approximation for obtaining carrier depth profiles inside the initial depletion region of a semiconductor through the combined use of the layer‐removal technique andC‐Vprofile measurements. This method has been successfully demonstrated through simulatedC‐Vprofile data created from a known Gaussian distribution of Si‐implanted GaAs.

ISSN:0003-6951    

DOI:10.1063/1.102656

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We propose a new quantum‐effect electronic device which consists of two one‐dimensional electron waveguides which, over a certain interaction length, come in close proximity to each other so that coherent quantum mechanical tunneling can take place between them. The degree of coupling between the two waveguides is controlled by modulating, through the field‐effect action of a gate, the height of the potential energy barrier which separates them. If an electron wave packet is injected into this device through one of the waveguides, then the probability density of the electron wave function will oscillate back and forth between the two waveguides as the packet advances. The gate voltage can be adjusted to achieve complete electron transfer at either of the two waveguides at the output of the device. The device, therefore, behaves as a current switch. In analogy with the optical dual‐channel directional coupler and the microwave dual‐guide multihole coupler, we call this device a quantum field‐effect directional coupler. First‐order calculations indicate that this device can be fabricated with state‐of‐the‐art nanolithography.

ISSN:0003-6951    

DOI:10.1063/1.102657

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have made the first magnetotransport measurements of two‐dimensional holes confined to GaSb in modulation‐doped AlSb/GaSb heterostructures. The Shubnikov–de Haas oscillations in GaSb‐AlSb heterostructures reflect the influence of strain as well as the symmetry of the confinement potential on the hole levels. We have also observed the quantized Hall effect in asymmetric single quantum wells.

ISSN:0003-6951    

DOI:10.1063/1.102659

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the dependence of the current‐voltage characteristics of AlGaAs/GaAs and AlGaAs/InGaAs resonant tunneling diodes (RTDs) on spacer layer thickness. The measured peak to valley current ratio of the RTDs studied here is shown to improve while the current density through the RTDs decreases with increasing spacer layer thickness below a critical value. We find significant differences in the effect of the spacer layer thickness between AlGaAs/InGaAs and AlGaAs/GaAs RTDs, which we believe to be related to the relative quasi‐bound state energies of the two systems.

ISSN:0003-6951    

DOI:10.1063/1.102660

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

(AlAs)1/2(GaAs)1/2fractional‐layer superlattices (FLSs) are grown on a (001) GaAs substrate, tilted slightly in the [1¯10] direction using metalorganic chemical vapor deposition. The periodic structures are analyzed by x‐ray superlattice satellite diffraction. The results suggest that the step flow mode from monolayer step is a dominant crystal growth process. However, the satellite intensities drastically decrease under heavy Si impurity doping conditions (n>2×1017cm−3), showing that impurity‐induced disordering occurs during fractional‐layer growth. The growth mechanism under impurity doping conditions is also discussed.

ISSN:0003-6951    

DOI:10.1063/1.102661

出版商:AIP    

年代:1990

数据来源: AIP