Sb-capping and decapping of MBE-grown GaSb(100)

We present a study of GaSb(100) surfaces grown by molecular beam epitaxy, protected by an Sb cap during ambient storage, and annealed in ultra-high vacuum. The surface structure, composition and electronic transitions are investigated with low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectroscopy. Successful Sb-decapping is achieved by annealing at 300° C for 30 min. It leads to a (2 × 3)−c(2 × 6) reconstructed surface with less residual damage and higher Sb concentration than surfaces prepared by sputtering and annealing.     

Existence and atomic arrangement of microtwins in CdTe epilayers grown on GaAs (211) B substrates

Selected area electron diffraction pattern (SADP) and high-resolution transmission electron microscopy (HRTEM) measurements were carried out to investigate the existence and the atomic arrangement of microtwins in CdTe epilayers grown on GaAs (211) B substrates by using molecular beam epitaxy. The SADP results showed that an epitaxial relationship between the CdTe epilayer and the GaAs substrate was formed. The lattice of the CdTe (211) tilts about 2° with respect to the GaAs (211) B substrate about the CdTe [110]∥GaAs [110] common zone axis. The HRTEM images showed that microtwins were formed in the CdTe epilayers. A possible atomic arrangement of the microtwins is presented on the basis of the HRTEM result. The present observations can help to improve understanding of the microstructural properties in CdTe epilayers grown on GaAs substrates.     

InSb(211)A,B表面电子结构特性

采用散射理论的格林函数方法计算了InSb(211)A,B两类表面的电子结构,分别给出了两类表面的表面投影能带结构,分析了各表面态的轨道特性和色散特性;并在此基础上讨论了两类表面的稳定性;计算结果和实验结果定性的相符合. 关键词：     

A method to extend wavelength into middle-wavelength infrared based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified In As Sb quantum well, Ga Sb is replaced with Al Sb/Al Ga Sb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.     

Performance of dual-band short-or mid-wavelength infrared photodetectors based on InGaAsSb bulk materials and InAs/GaSb superlattices

In this paper,we demonstrate bias-selectable dual-band short-or mid-wavelength infrared photodetectors based on In_(0.24)Ga_(0.76)As_(0.21)Sb_(0.79)bulk materials and InAs/GaSb type-II superlattices with cutoff wavelengths of 2.2μm and 3.6μm,respectively.At 200 K,the short-wave channel exhibits a peak quantum efficiency of 42%and a dark current density of5.93×10~(-5)A/cm~2at 500 mV,thereby providing a detectivity of 1.55×10~(11)cm·Hz~(1/2)/W.The mid-wave channel exhibits a peak quantum efficiency of 31%and a dark current density of 1.22×10~(-3)A/cm~2at-300 mV,thereby resulting in a detectivity of 2.71×10~(10)cm·Hz~(1/2)/W.Moreover,we discuss the band alignment and spectral cross-talk of the dual-band n-i-p-p-i-n structure.     

Diffusion of W on A W(211) plane

The diffusion of W on a (211) plane of a W field emitter has been re-examined by means of the fluctuation autocorrelation method. Diffusion along channels yielded E = 16.8 ± 0.5 kcal, D₀ = (3 ± 1) × 10⁻⁵ cm² s⁻¹. For diffusion across channels E =6.6 kcal, D₀ = 4 × 10⁻⁹cm² s⁻¹ at T < 752 K, and E = 24 kcal, D₀ = 5 × 10⁻⁴ cm² s⁻¹ at T > 752 K. The results for diffusion along channels yield E and D₀ values intermediate between recent results by Wang and Ehrlich [Surf. Sci. 206 (1988) 451] using field ion microscopy (E = 19 kcal, D₀ = 7.7 × 10⁻³ cm² s⁻¹) and Tringides and Gomer [J. Chem. Phys. 84 (1986) 4049], using the same method as the present work but a larger slit (E = 13.3 kcal, D₀ = 7 × 10⁻⁷ cm² s⁻¹). The results for cross channel diffus good agreement with those of Tringides and Gomer below 752 K, where these authors stopped. The new high temperature results suggest that the channel wall exchange mechanism postulated by Tringides and Gomer for cross channel diffusion at low T gives way to diffusion by climbing over the channel walls with higher E but also higher D₀ above 752 K. Possible reasons for the discrepancies between these three sets of results and the absence of cross channel diffusion in the work of Wang and Ehrlich are briefly discussed.     

Long-wavelength luminescence from GaSb quantum dots grown on GaAs substrates

Self-assembled GaSb quantum dots (QDs) with a photoluminescence wavelength longer than 1.3 μm were successfully grown by suppressing the replacement of As and Sb on the surface of the GaSb QDs. This result means that GaSb can thus join InAs or GaInAs as a suitable material for QD lasers for optical communications.     

A statistical model for oxygen adsorption on W (211)

A series of previous experimental investigations revealed that oxygen adsorption on a W (211) surface causes, at $\text{θ =}\text{1}\text{2}$, a 2 × 1 LEED pattern whose half order spots are streaked at lower coverages and become continuously weaker at $\text{θ >}\text{1}\text{2}\text{until at}\text{θ = 1}$ a 1 × 1 structure is formed. A model is proposed wherein the configuration of the adsorbed atoms with respect to each other is governed by a set of anisotropic interactions between neighbouring particles. These (three) interaction energies have magnitudes between kT and 2kT. The equilibrium arrangements for various coverages were simulated by means of the Monte Carlo technique, and the corresponding LEED patterns (angular profiles) were evaluated by using the kinematic approximation. Good agreement with experimental data is obtained for the variation of the relative intensity as well as of the breadth of the half order LEED spots, without the need for any further assumptions on the mechanism of the formation of the ordered adsorbed layers.     

Epitaxial films of GeSi, AlGaN, and GaSb and GaSb/InAs superlattices on substrates of fianite

Fianite is a single crystal of cubic solid solutions based on zirconium dioxide (ZrO₂) or hafnium dioxide (HfO₂) with stabilizing oxides of yttrium, scandium, and lanthanides. It is characterized by a unique combination of physical and chemical properties, making it a promising material for wide use in electronics. In this work, we consider new uses of fianite as a monolith substrate for obtaining Ge, GeSi, AlGaN, and GaSb epitaxial films and GaSb/InAs superlattices.     

Electron-beam-excited lasers based on A2B6 compounds (review)

The literature on electron-beam-pumped semiconductor lasers (EPSLs) based on A²B⁶ compounds is reviewed. Recent advances in the development of EPSLs in the Nineties are reflected. The literature data on the output parameters of these EPSLs are systematized. Basic parameters and characteristics of EPSLs their hardware realization, the properties of active media, and the mechanisms of amlification and degradation are discussed. The works on the use of EPSLs for pumping of other active media are reviewed. Institute of Semiconductor Engineering RWTH, 55, Templergraben, Aachen, D-52056, Germany (permanent address: B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 601–618, September–October, 1999     

GaSb(100)的表面再构

用低能电子衍射(LEED),光电子能谱(XPS和UPS)研究GaSb(100)表面的各种再构:c(2×6),(1×3)和(2×3)。所有这三种再构表面都以有失列的Sb原子结尾。在Sb气氛中退火可使分子束外延(MBE)制备的、表面Sb原子形成二聚物的c(2×6)再构和离子轰击加退火(IBA)制备的、表面存在Ga岛的(2×3)再构均变为简单的(1×3)再构。 关键词：     

Theoretical study of the stability of 5d dimers on W(211) and Ta(211)

It is known experimentally that Re₂ dimers are stable on W(211) whereas they are unstable on W(110). In the framework of the model previously used for 5d dimers on W(110), we explain this different behaviour by the larger coordination number on the (211) face, which tends to increase the stabilizing role of the one electron contribution and to decrease the destabilizing role of electronic correlations. A maximum of stability is obtained for dimers in the middle of the 5d series.     

Sputtering of A 3 B 5 materials (GaP, GaAs, GaSb, InP, and InSb) by 2-to 14-keV N 2 + ions

Investigations of the general characteristics and distinctive features of sputtering of A ³ B ⁵ materials (GaP, GaAs, GaSb, InP and InSb) under bombardment with N ₂ ⁺ ions have been carried out. From the experimental data, dependences of the sputtering yield of these materials on the incidence angle and ion energy have been obtained and the surface relief patterns produced by target etching have been studied. It has been shown that the dependence on energy of the sputtering yield for GaP, GaAs, and InP can be adequately described by the Haffa-Switkovski formula for binary materials and Yudin’s approximation for elemental targets. Sputtering of GaSb and InSb proceeds in the surface layer recrystallization mode, and the sputtering yield agrees with calculations based on Onderlinden’s model. From a comparison of the experimental and calculated dependences, the surface bonding energies have been determined.     

Formation of pyramid-like nanostructures in MBE-grown Si films on Si(001)

The growth of Si homoepitaxial layers on Si(001) substrates by molecular beam epitaxy is analyzed for a set of growth conditions in which diverse nanometer-scale features develop. Using Si substrates prepared by exposure to HF vapor and annealing in ultra-high vacuum, a rich variety of surface morphologies is found for different deposited layer thicknesses and substrate temperatures in a reproducible way, showing a critical dependence on both. Arrays of 3D islands (truncated pyramids), percolated ridge networks, and square pit (inverted pyramid) distributions are observed. We analyze the obtained arrangements and find remarkable similarities to other semiconductor though heteroepitaxial systems. The nanoscale entities (islands or pits) display certain self assembly and ordering, concerning size, shape, and spacing. Film growth sequence follows the ‘islands–coalescence–2D growth’ pathway, eventually leading to optimum flat morphologies for high enough thickness and temperature.     

Investigation of active-region doping on InAs/GaSb long wave infrared detectors

The eight-band κ·p model is used to establish the energy band structure model of the type-II InAs/GaSb superlattice detectors with a cut-off wavelength of 10.5μm,and the best composition of M-structure in this type of device is calculated theoretically.In addition,we have also experimented on the devices designed with the best performance to investigate the effect of the active region p-type doping temperature on the quantum efficiency of the device.The results show that the modest active region doping temperature(Be:760℃)can improve the quantum efficiency of the device with the best performance,while excessive doping(Be:>760℃)is not conducive to improving the photo response.With the best designed structure and an appropriate doping concentration,a maximum quantum efficiency of 45% is achieved with a resistance-area product of 688?·cm^2,corresponding to a maximum detectivity of 7.35×10^11cm·Hz^1/2/W.     

The effect of hydrogenation in HgxCd1 − xTe thin films grown on p-CdTe (211) B substrates

Fourier transform infrared (FTIR) transmission, Hall effect, and nuclear resonance reaction measurements have been carried out to investigate the effect of hydrogenation on the deep levels and the hydrogen depth profiling in nominally undoped Hg_xCd_{1 − x}Te layers grown on undoped p-CdTe (211) B-orientation substrates by molecular beam epitaxy. After hydrogenation, the FTIR spectra showed that the transmittance intensity increased in comparison to that of the as-grown Hg_xCd_{1 − x}Te and that the absorption edge shifted to the short wavelength range. Hall effect measurements showed that the carrier concentration decreased and the mobility increased after hydrogenation. After hydrogenation, p-type Hg_xCd_{1 − x}Te is converted to n-type Hg_xCd_{1 − x}Te with high resistivity. Nuclear resonance raaction measurements show that the concentration and the penetration depth of the hydrogen atom in n-Hg_0.77Cd_0.23Te are 3.5% and 640 Å, respectively. The areal density of the hydrogen-containing layer at the surface of the hydrogenated n-Hg_0.77Cd_0.23Te film is 4.39 × 10¹⁵ atoms/cm². These results indicate that hydrogen atoms not only effectively passivate impurities or defects in the Hg_xCd_{1 − x}Te film but also change the carrier type of p-Hg_xCd_{1 − x}Te.