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31 Aug 1992

Volume 61, Issue 9, pp. 1013-1139

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Improving the performance of semiconductor ring lasers by controlled reflection feedback

J. P. Hohimer, G. A. Vawter, D. C. Craft, and G. R. Hadley

Appl. Phys. Lett. 61, 1013 (1992); http://dx.doi.org/10.1063/1.107700 (3 pages) | Cited 18 times

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We report a tenfold increase in the lasing output of single‐output Y‐junction semiconductor ring lasers by reducing the end‐facet reflection feedback. Controlled reflection feedback is also shown to be a means for promoting unidirectional lasing in dual‐output ring lasers. Finally, we show that the counterpropagating ring modes are strongly coupled by gain competition.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Theoretical analysis of dynamic response of asymmetric dual quantum well lasers

Sotomitsu Ikeda and Akira Shimizu

Appl. Phys. Lett. 61, 1016 (1992); http://dx.doi.org/10.1063/1.107701 (3 pages) | Cited 8 times

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Dynamic responses of the photon and carrier densities in an asymmetric dual quantum well laser which exhibits wavelength switching are analyzed theoretically. The laser consists of two different quantum wells isolated by a high and/or thick barrier layer that results in an inhomogeneous carrier injection into the two wells. The calculated pulse response at a voltage of the dual‐wavelength lasing shows that the emission of the shorter wavelength light precedes that of the longer wavelength light by a nanosecond, in agreement with recent experimental results.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Observation of the focusing of x‐ray transition radiation using cylindrical optics

M. A. Piestrup, D. G. Boyers, C. I. Pincus, Qiang Li, A. H. Ho, X. K. Maruyama, D. D. Snyder, D. M. Skopik, R. M. Silzer, M. J. Moran, and G. B. Rothbart

Appl. Phys. Lett. 61, 1019 (1992); http://dx.doi.org/10.1063/1.107702 (3 pages) | Cited 1 time

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We have measured the profile of x rays generated by a transition radiator and focused by simple cylindrical optics. Soft x rays with photon energies between 1 and 4 keV were generated by a 93‐MeV electron beam striking a stack of eight foils of 3.5‐μm‐thick mylar. These x rays were emitted in an annular cone and were collected by a quartz cylinder which focused the x rays to a 0.5‐mm‐diam spot at a distance of 1.35 m from the transition radiator.
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41.50.+h X-ray beams and x-ray optics
41.60.-m Radiation by moving charges
07.85.-m X- and γ-ray instruments

New principle for optical filters

R. Magnusson and S. S. Wang

Appl. Phys. Lett. 61, 1022 (1992); http://dx.doi.org/10.1063/1.107703 (3 pages) | Cited 226 times

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A theoretical characterization of the guided‐mode resonance properties of planar dielectric waveguide gratings is presented. Efficient exchange of energy between forward and backward propagating diffracted waves is shown to be possible with smooth line shapes. The linewidths of the resonances can be controlled by the grating modulation amplitude. Due to the inherent separation between the TE and TM modes associated with the waveguide grating, these elements can provide polarization separation. Applications to polarization sensitive filtering and to electro‐optic switching are suggested. The guided‐mode resonance filter represents a basic new optical element.
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42.25.-p Wave optics
42.79.-e Optical elements, devices, and systems

Sidelobe suppression in an acousto‐optic filter with a raised‐cosine interaction strength

D. A. Smith and J. J. Johnson

Appl. Phys. Lett. 61, 1025 (1992); http://dx.doi.org/10.1063/1.107704 (3 pages) | Cited 20 times

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We have demonstrated a 10‐dB reduction in the intensity sidelobes of an apodized‐interaction‐strength guided‐wave acousto‐optic filter with a center passband of 1530 nm. Acoustic‐intensity weighting was achieved by launching a surface acoustic wave (SAW) beam in a straight acoustic waveguide, and gradually transferring this SAW intensity to the active device, and back out, by evanescent‐wave coupling across a 20 μm barrier over a 19‐mm interaction length. The intensity sidelobe was −5 dB for an unapodized filter with abrupt onset and cutoff of the interaction, but sidelobes were reduced to at most −15 dB for a SAW intensity with raised‐cosine weighting. A conversion efficiency of 97% was achieved with 80 mW input power for the 2.0‐nm‐wide apodized filter.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Jq Acousto-optical devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

C60 photoluminescence spectra related to gas adsorption

Tienan Zhao, Jinqing Liu, Yuliang Li, and Daoben Zhu

Appl. Phys. Lett. 61, 1028 (1992); http://dx.doi.org/10.1063/1.107705 (3 pages) | Cited 12 times

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The influence of surrounding gas pressure upon PL spectra of C60 is observed. The relationship between intensity of PL spectra and pressure agrees well with the Langmuir formula of a monomolecular adsorption layer. This phenomenon is attributed to the fact that the disturbance of molecules adsorbed on C60 lowers the symmetry of C60 and reduces the inhibition of the electronic transition, hence influencing PL emission.
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78.55.Hx Other solid inorganic materials
71.70.-d Level splitting and interactions
73.20.-r Electron states at surfaces and interfaces

Nitrogen and oxygen incorporation during rapid thermal processing of Si in N2O

A. E. T. Kuiper, H. G. Pomp, P. M. Asveld, W. Arnold Bik, and F. H. P. M. Habraken

Appl. Phys. Lett. 61, 1031 (1992); http://dx.doi.org/10.1063/1.107706 (3 pages) | Cited 25 times

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Using a special detector setup in elastic recoil detection measurements, the incorporation of nitrogen during rapid thermal processing of Si(100) in N2O has been quantified for the first time. During oxidation at 1150 °C, the equivalent of a monolayer of silicon nitride is formed at the SiO2/Si interface. This retards the oxidation rate but it does not inhibit further oxide growth, which implies that gate oxides with thicknesses up to several tens of nm can be produced in N2O.
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81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Fx Diffusion; interface formation

Structure of GaAs=GaSb incoherent interface after epitaxial growth

A. Bourret and P. H. Fuoss

Appl. Phys. Lett. 61, 1034 (1992); http://dx.doi.org/10.1063/1.107707 (3 pages) | Cited 29 times

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The structure of GaAs=GaSb(001) incoherent interface has been studied by grazing incidence x‐ray scattering. The interface is periodic with a square array of edge dislocations. It is shown that the interface is nonplanar with 2–4 GaAs monolayers protruding in the GaSb epilayer at the dislocation core. This corrugated interface does not increase the strain energy by a large factor. Two possible mechanisms are suggested for the interface formation of large misfit epitactic growth: a stress induced mechanism or the presence of an ordered intermediate 2D layer.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)

Nitrogen‐induced amorphization of Ti‐Zr powders during mechanical alloying

K. Aoki, A. Memezawa, and T. Masumoto

Appl. Phys. Lett. 61, 1037 (1992); http://dx.doi.org/10.1063/1.107708 (3 pages) | Cited 15 times

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A mixture of elemental powders of Ti and Zr, which exhibit the complete solid solubility, has been mechanically alloyed by a high‐energy ball mill, at room temperature, under a controlled nitrogen atmosphere. The products were characterized by x‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and chemical analysis. Nanocrystalline fcc type c‐TiZrN0.9 powders were prepared by MA in 2 MPa of nitrogen gas. On the contrary, amorphous a‐TiZrN0.3 alloy powders were synthesized by MA in 0.04 MPa of nitrogen gas.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.30.Bx Phase diagrams of metals, alloys, and oxides
61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals

Ballistic electron emission microscopy of laterally patterned microstructures

A. Davies, J. G. Couillard, and H. G. Craighead

Appl. Phys. Lett. 61, 1040 (1992); http://dx.doi.org/10.1063/1.107709 (3 pages) | Cited 8 times

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Ballistic electron emission microscopy (BEEM) has been used to investigate and image microfabricated Au/SiGe features. Electron beam lithography and dry etching were used to construct arrays of holes in a SiO2 layer and etched indentations in SiGe. The electronic transport properties of the fabricated structure and adjacent unpatterned region were then characterized and imaged with BEEM. These studies demonstrate that BEEM is capable of resolving transport variation with 1–2 nm spatial resolution and can be used to study the microscopic effects of reactive ion etching. The types of imaging contrast and subsurface electron transport information obtainable from BEEM cannot be obtained by other scanned beam or scanned probe techniques.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
61.80.Jh Ion radiation effects

Growth of face‐centered‐cubic single crystals of C60 from boiling benzene

Yositaka Yosida, Takeshi Arai, and Hiroyoshi Suematsu

Appl. Phys. Lett. 61, 1043 (1992); http://dx.doi.org/10.1063/1.107710 (2 pages) | Cited 10 times

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We report a new synthesis technique of face‐centered‐cubic single crystals of C60 with a macroscopic dimension of 0.3×0.3×0.5 mm3. The crystals are grown from a benzene heated above 80 °C. The mosaic spread of the crystal is about 0.5°.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.10.Dn Growth from solutions

Twofold efficiency improvement in high performance AlGaInP light‐emitting diodes in the 555–620 nm spectral region using a thick GaP window layer

K. H. Huang, J. G. Yu, C. P. Kuo, R. M. Fletcher, T. D. Osentowski, L. J. Stinson, M. G. Craford, and A. S. H. Liao

Appl. Phys. Lett. 61, 1045 (1992); http://dx.doi.org/10.1063/1.107711 (3 pages) | Cited 66 times

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AlGaInP light‐emitting diodes (LEDs) with external quantum efficiencies ≥6% and luminous performance of 20 lm/W have been fabricated. These LEDs are twice as efficient as previously reported AlGaInP devices throughout the spectral region from green (555 nm) to red‐orange (620 nm) owing to a thicker GaP window layer (45 vs 15 μm). Using hydride vapor phase epitaxy, thick GaP window layers were grown on top of AlGaInP double heterostructures grown by organometallic vapor phase epitaxy. The efficiency of the LEDs was found to improve as the thickness of the window layer was increased from 9 to 63 μm. This improvement is predicted by a simple model that considers the benefit of enhanced emission through the sides of the thick window. The effect of emission wavelength on quantum efficiency and luminous performance for AlGaInP LEDs with a 45 μm thick window has been studied.
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85.60.Jb Light-emitting devices
81.15.Kk Vapor phase epitaxy; growth from vapor phase

High transconductance in‐plane‐gated transistors

A. D. Wieck and K. Ploog

Appl. Phys. Lett. 61, 1048 (1992); http://dx.doi.org/10.1063/1.107712 (3 pages) | Cited 14 times

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Focused‐ion‐beam written one‐dimensional field‐effect transistors are fabricated and characterized at room temperature. By writing these in‐plane‐gated channels with geometrical widths of 0.2–1.1 μm in heterostructures, we obtain one‐dimensional transconductances of up to 170 μS for two channels in parallel. We determine the effective width of the channels, which ranges between 790 nm and zero, being still reproducibly tunable at a few nanometers. The reproducibility in fabrication already of the prototypes presented here is sufficient for integration applications. We observe current densities, which can only be explained by a strong velocity overshoot of the electrons and promises excellent high‐frequency behavior of the device. The in‐plane‐gate transistor does not need any alignment and can easily be interconnected and integrated with a writing speed exceeding 106 devices per s.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer

pnp resonant tunneling light emitting transistor

J. Genoe, C. Van Hoof, K. Fobelets, R. Mertens, and G. Borghs

Appl. Phys. Lett. 61, 1051 (1992); http://dx.doi.org/10.1063/1.107713 (3 pages) | Cited 6 times

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A pnp bipolar resonant tunneling transistor is realized using a base consisting of an n‐type modulation doped quantum‐well layer next to a double‐barrier tunneling structure. Electrons are injected from the quantum‐well base layer into the tunneling structure, leading to quantum‐well light emission when they recombine with holes from the emitter. This optical output, which is modulated by the base voltage, persists in the negative differential resistance region of the current‐voltage characteristics where the hole current is in oscillation. This opens possibilities for using this transistor as a high frequency electro‐optical heterodyne convertor.
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85.60.Jb Light-emitting devices
85.30.Pq Bipolar transistors
73.40.Gk Tunneling

Influence of hydrogen on the step flow growth of GaAs on vicinal surfaces by gas‐source migration enhanced epitaxy

H. Asahi, T. Hisaka, S. G. Kim, T. Kaneko, S. J. Yu, Y. Okuno, and S. Gonda

Appl. Phys. Lett. 61, 1054 (1992); http://dx.doi.org/10.1063/1.107714 (3 pages) | Cited 6 times

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Step flow growth of GaAs on the vicinal surfaces by gas‐source migration enhanced epitaxy (MEE), the combination of gas‐source molecular beam epitaxy and MEE, is studied with the reflection high‐energy electron diffraction (RHEED) intensity oscillation. It is found that the use of the thermally cracked AsH3 instead of solid As (As4) as an As source enhances step flow growth of GaAs on the (001) surface misoriented toward the [110] direction. The same tendency is also observed in the MEE growth using As4 under the hydrogen supply. It is considered that the enhancement of step flow growth in the gas‐source MEE is caused by the hydrogen atoms terminated at the steps.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Schottky barrier inhomogeneity caused by grain boundaries in epitaxial Al film formed on Si(111)

Y. Miura, K. Hirose, K. Aizawa, N. Ikarashi, and H. Okabayashi

Appl. Phys. Lett. 61, 1057 (1992); http://dx.doi.org/10.1063/1.107715 (3 pages) | Cited 12 times

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Epitaxial Al contacts on Si(111) are fabricated by electron beam evaporation at various substrate temperatures around 250 °C. They are observed by high‐resolution transmission electron microscopy. Schottky barrier heights (SBHs) of the contacts are measured using current‐voltage and capacitance‐voltage methods. In the case of single‐crystalline Al film, the SBH does not change and its spatial distribution remains homogeneous up to an annealing temperature of 550 °C. In contrast with this, for an epitaxial Al film containing grain boundaries, the spatial distribution of the SBH becomes inhomogeneous above 400 °C. This is attributed to Si diffusion along the grain boundaries in the Al film.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
68.55.-a Thin film structure and morphology

In situ infrared and mass spectroscopic study of the reaction of WF6 with hydrogenated amorphous silicon

Toshimasa Wadayama, Hironobu Shibata, Tsutomu Ohtani, and Aritada Hatta

Appl. Phys. Lett. 61, 1060 (1992); http://dx.doi.org/10.1063/1.107716 (3 pages) | Cited 3 times

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The reaction process of tungsten hexafluoride (WF6) with photochemically deposited hydrogenated amorphous silicon was studied by polarization modulation infrared spectroscopy and quadruple mass spectrometry. Infrared absorption bands due to species (SiH3 and SiH2) incorporated in the hydrogenated amorphous silicon were decreased in intensity during exposure of WF6. The reduction rate was faster for the SiH3 species than for the SiH2 species. The mass spectrometric analysis revealed that evolution of hydrogen into the gas phase took place prior to that of silicon fluorides. These results strongly suggest that WF6 reacts preferentially with the SiH3 species present in the hydrogen‐rich surface layer.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Visible photoluminescence of Zn‐doped CuAlS2

Igor Aksenov and Katsuaki Sato

Appl. Phys. Lett. 61, 1063 (1992); http://dx.doi.org/10.1063/1.107717 (3 pages) | Cited 10 times

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The observation of a very intense blue and green photoluminescence from low‐resistivity CuAlS2 crystals, grown by chemical vapor transport and subsequently doped with Zn, is reported. The emission is strong even at room temperature, the color of emission being dependent on Zn‐doping conditions. Results obtained suggest that the CuAlS2 compound can be considered as a perspective material for blue and green light‐emitting device realization.
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78.55.Et II-VI semiconductors
71.55.Gs II-VI semiconductors
61.72.up Other materials

Laser‐driven boron diffusion into a Si epitaxial layer from a p+ boron‐doped Si substrate

K. M. Kim, S. N. Mei, M. J. Saccamango, S. F. Chu, R. J. von Gutfeld, and D. R. Vigliotti

Appl. Phys. Lett. 61, 1066 (1992); http://dx.doi.org/10.1063/1.107718 (3 pages)

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Experiments are described in which ∼0.2‐s‐wide argon laser pulses are incident on a 6‐μm‐thick n− Si epitaxial layer. Local melting and refreezing of both the layer and a small volume of the underlying p+ boron‐doped Si substrate occur. In the molten phase, boron diffusion from the substrate is sufficient to make a low resistance path between the front surface and the substrate, with a nearly uniform dopant concentration of 5×1018/cm3. The melted/recrystallized front surface diameter is ∼50 μm. Unique features and applications of this type of substrate contacting are discussed.
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85.40.Hp Lithography, masks and pattern transfer
61.72.uf Ge and Si
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
66.30.J- Diffusion of impurities

Evidence for quantum well asymmetry in optical absorption

P. M. Young and H. Ehrenreich

Appl. Phys. Lett. 61, 1069 (1992); http://dx.doi.org/10.1063/1.107719 (3 pages) | Cited 9 times

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Some previously unexplained features of the experimentally determined optical spectra of GaAs/Ga1−xAlxAs heterostructures are theoretically explained in terms of unintentionally introduced asymmetries in the shape of semiconductor quantum wells which break the usual optical selection rules. Various mechanisms that may be responsible for well asymmetries are suggested. Their measurement may be a useful characterization tool in quantum well fabrication.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors

Enhanced carrier densities and device performance in piezoelectric pseudomorphic high‐electron mobility transistor structures

J. Sánchez‐Dehesa, J. L. Sánchez‐Rojas, C. Lopez, and R. J. Nicholas

Appl. Phys. Lett. 61, 1072 (1992); http://dx.doi.org/10.1063/1.107694 (3 pages) | Cited 16 times

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The addition of a piezoelectric field in AlGaAs/InGaAs/GaAs HEMT structures is shown to lead to enhanced electron densities and hence improved device performance. Growth of a strained InxGa1−xAs layer is in [111]A direction causes a piezoelectric field to be built into the quantum well of a pseudomorphic HEMT, which opposes the electric field due to charge transfer and hence lowers the confinement energy. This leads to carrier densities 50% larger than in equivalent [100] structures, with the wave function also spaced further away from the dopant impurities and the well interfaces. We expect these factors to give improved device performance.
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73.50.Dn Low-field transport and mobility; piezoresistance
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Organometallic vapor phase epitaxy of CoGa on (100)GaAs

F. Maury, A. A. Talin, H. D. Kaesz, and R. S. Williams

Appl. Phys. Lett. 61, 1075 (1992); http://dx.doi.org/10.1063/1.107695 (3 pages) | Cited 4 times

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We report the first epitaxial growth of CoGa thin films on (100)GaAs substrates by organometallic chemical vapor deposition. The separate sources (η5‐C5H5)Co(CO)2 and Et3Ga were mixed in a stream of carrier gas and decomposed in a conventional cold wall epitaxial reactor between 260 and 300 °C under atmospheric pressure. A typical growth rate of 1 μm/h was achieved and the film composition could be directly monitored from the gas phase composition. The Co‐rich films have the α‐Co metal structure and react with GaAs at 500 °C to form CoAs. By contrast, Ga‐rich β‐CoGa films were lattice matched on (100)GaAs and were found to be thermodynamically stable at 500 °C. This work demonstrates that organometallic vapor phase epitaxy is also a suitable technique for the fabrication of buried metal/semiconductor heterostructures.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.60.Dv Thermal stability; thermal effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Dependence of lifetime on surface concentration of copper and iron in silicon wafers

L. Zhong and F. Shimura

Appl. Phys. Lett. 61, 1078 (1992); http://dx.doi.org/10.1063/1.107696 (3 pages) | Cited 6 times

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Minority‐carrier lifetime after oxidation is investigated with a laser‐microwave photoconductance (LM‐PC) method for silicon wafers deliberately contaminated with Cu or Fe of different surface concentrations. The secondary ion mass spectroscopy (SIMS) depth profile clearly correlate the effect of those impurities on the bulk and surface components, which are obtained with a recently developed algorithm, of the effective lifetime. Copper impurities diffused from the wafer surface segregate at the SiO2/Si interface and near‐interface region, and the surface component becomes dominant at high‐surface contaminations. On the other hand, most of the iron segregates in the oxide layer and the residual iron diffuses into the bulk region, and therefore the bulk component dominates the effective lifetime.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Intersubband transitions in quantum well heterostructures with delta‐doped barriers

Lakshmi N. Pandey and Thomas F. George

Appl. Phys. Lett. 61, 1081 (1992); http://dx.doi.org/10.1063/1.107674 (3 pages) | Cited 13 times

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A single quantum well doped by a negative delta‐function potential (δ‐potential) in the barrier regions is analyzed in terms of the optical transitions in between subbands. The first two states of the quantum well do not change at all as a function of the strength of the δ‐potential up to a certain value, whereas the third one gets lowered almost exponentially. An important point is that the δ‐potential brings a state from the continuum to the bound region. There is a range of the strength of the δ‐potential during which the transition energy for the first to second state decreases rapidly, and at a certain strength the first and second states disappear, and the third and fourth, which have been brought from the continuum, take their places. The oscillator strengths of the allowed transitions have a kind of oscillatory behavior in that range.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.40.Gk Tunneling
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Growth of a delta‐doped silicon layer by molecular beam epitaxy on a charge‐coupled device for reflection‐limited ultraviolet quantum efficiency

Michael E. Hoenk, Paula J. Grunthaner, Frank J. Grunthaner, R. W. Terhune, Masoud Fattahi, and Hsin‐Fu Tseng

Appl. Phys. Lett. 61, 1084 (1992); http://dx.doi.org/10.1063/1.107675 (3 pages) | Cited 22 times

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We have used low‐temperature silicon molecular beam epitaxy to grow a δ‐doped silicon layer on a fully processed charge‐coupled device (CCD). The measured quantum efficiency of the δ‐doped backside‐thinned EG&G Reticon CCD is in agreement with the reflection limit for light incident on the back surface in the spectral range of 260–600 nm. The 2.5 nm silicon layer, grown at 450 °C, contained a boron δ‐layer with surface density ∼2×1014 cm−2. Passivation of the surface was done by steam oxidation of a nominally undoped 1.5 nm Si cap layer. The UV quantum efficiency was found to be uniform and stable with respect to thermal cycling and illumination conditions.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.30.Tv Field effect devices
85.60.Gz Photodetectors (including infrared and CCD detectors)
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