InGaP/GaAs HBT费米统计律下的数值模拟计算

用费米分布函数对HBT结构中载流子的分布进行了计算,与常用的玻尔兹曼统计律得到的载流子分布进行了比较分析。同时在热场发射－扩散模型的基础上,用两种方法得到的载流子分布分别对InGaP/GaAsHBT进行了数值模拟计算和分析。     

InGaP/GaAs微波HBT器件与电路研究及应用进展

概述了近年来微波InGaP/GaAs异质结双极晶管(HBT)器件和集成电路的研究和应用现状,着重阐述了HBT器件的热设计、降低偏移电压、离子注入隔离、湿法腐蚀,以及用于电路设计的等效电路模型等关键问题.     

Investigation of the photoluminescence and modification of InGaP/GaAs/InGaAs heterostructures by near-field scanning microscopy

This study deals with the local spectroscopy and modification of semiconducting InGaP/GaAs/InGaAs quantum-well heterostructures by near-field scanning optical microscopy. The spatial distribution of the photoluminescence intensity in these structures is investigated and spatial nonuniformity of the photoluminescence is observed as a result of the nonuniform properties of the InGaP layers. It is shown for the first time that local quenching of the photoluminescence may be achieved by optically induced impurity diffusion near the quantum well, and this may be utilized to develop low-dimension semiconducting devices. Pis’ma Zh. Tekh. Fiz. 23, 20–25 (August 26, 1997)     

Effects of growth parameters on the structural and optical properties of InP/InGaP quantum structures for 808-nm-wavelength emissions

InP/InGaP quantum structures with 808-nm-wavelength emissions were grown on semi-insulating GaAs (100) substrates via migration-enhanced molecular beam epitaxy. The effects of the growth conditions on the structural and optical properties of the InP/InGaP quantum structures were investigated. The scanning electron microscopy and atomic force microscopy images showed that the two-dimensional InP/InGaP quantum structures were transited to one-dimensional structures with an increasing repetition cycle. The photoluminescence spectra showed that the optical properties of the InP/InGaP quantum structures were significantly affected by various migration-enhanced epitaxy repetition numbers and growth temperatures. These results can help improve understanding of the effects of growth parameters on the structural and optical properties of InP/InGaP quantum structures for 808-nm-wavelength emissions.     

Monolithic GaAs/InGaP nanowire light emitting diodes on silicon

Vertical light emitting diodes (LEDs) based on GaAs/InGaP core/shell nanowires, epitaxially grown on GaP and Si substrates, have been fabricated. The devices can be fabricated over large areas and can be precisely positioned on the substrates, by the use of standard lithography techniques, enabling applications such as on-chip optical communication. LED functionality was established on both kinds of substrate, and the devices were evaluated in terms of temperature-dependent photoluminescence and electroluminescence.     

Self-ordered nanostructures on patterned substrates

The formation of nanostructures during metalorganic vapor-phase epitaxy on patterned (001)/(111)B GaAs substrates is reviewed. The focus of this review is on the seminal experiments that revealed the key kinetic processes during nanostructure formation and the theory and modelling that explained the phenomenology in successively greater detail. Experiments have demonstrated that V-groove quantum wires and pyramidal quantum dots result from self-limiting concentration profiles that develop at the bottom of V-grooves and inverted pyramids, respectively. In the 1950s, long before the practical importance of patterned substrates became evident, the mechanisms of capillarity during the equilibration of non-planar surfaces were identified and characterized. This was followed, from the late 1980s, by the identification of growth rate anisotropies (i.e. differential growth rates of crystallographic facets) and precursor decomposition anisotropies, with parallel developments in the fabrication of V-groove quantum wires and pyramidal quantum dots. The modelling of these growth processes began at the scale of facets and culminated in systems of coupled reaction–diffusion equations, one for each crystallographic facet that defines the pattern, which takes account of the decomposition and surface diffusion kinetics of the group-III precursors and the subsequent surface diffusion and incorporation of the group-III atoms released by these precursors. Solutions of the equations with optimized parameters produced concentration profiles that provided a quantitative interpretation of the time-, temperature-, and alloy-concentration-dependence of the self-ordering process seen in experiments.     

Metamorphic InAs/InGaAs/InAlAs quantum wells with submonolayer InSb insertions emitted in the mid-infrared spectral range

Metamorphic InAs/InGaAs/InAlAs quantum wells with submonolayer InSb insertions have been grown for the first time by molecular beam epitaxy on GaAs (001) substrates using a graded InAlAs buffer layer with increasing In composition. The given nanoheterostructures demonstrate an intense photoluminescence at a wavelength of over of over 3 μm (80 K), which is shifted toward longer wavelengths as compared with that of the structures without InSb insertions.     

InAs/GaAs nanostructures grown on patterned Si(001) by molecular beam epitaxy

The potential benefit from the combination of the optoelectronic and electronic functionality of III-V semiconductors with silicon technology is one of the most desired outcomes to date. Here we have systematically investigated the optical properties of InAs quantum structure embedded in GaAs grown on patterned sub-micron and nanosize holes on Si(001). III-V material tends to accumulate in the patterned sub-micron holes and a material depletion region is observed around holes when GaAs/InAs/GaAs is deposited directly on patterned Si(001). By use of a 60?nm SiO(2) layer and patterning sub-micron and nanosize holes through the oxide layer to the substrate, we demonstrate that high optical quality InAs nanostructures, both quantum dots and quantum wells, formed by a two-monolayer InAs layer embedded in GaAs can be epitaxially grown on Si(001). We also report the power-dependent and temperature-dependent photoluminescence spectra of these structures. The results show that hole diameter (sub-micron versus nanosize) has a strong effect on the structural and optical properties of GaAs/InAs/GaAs nanostructures.     

Effect of temperature on optical and electronic properties of InGaP/InGaAIP multiple quantum wells

The optical and electronic properties in an InGaP/InGaAIP multiple quantum well (MQW) grown by using molecular-beam epitaxy utilizing the digital alloy technique were investigated through temperature-dependent photoluminescence (PL) measurements and numerical calculations. The high-resolution transmission electron microscopy images showed that the sample clearly displayed the InGaP wells and the InGaAIP barriers and separate confinement heterostructure layers. The PL measurements at various temperatures were performed to investigate the interband transitions of the InGaP/InGaAIP MQW. The electronic subband energies and the wavefunctions in the InGaP/InGaAIP MQW at several temperatures were determined by using a finite element method employing the standard 8-band k x p Lagrangian. The numerical results for optical interband transition energies from the ground state electron subband to the ground state heavy-hole subband of the InGaP/InGaAIP MQW at various temperatures were in reasonable agreement with the excitonic transition energies observed in the PL measurements.     

The influence of post-growth annealing on the optical properties of InAs quantum dot chains grown on pre-patterned GaAs(100)

We report on the effect of post-growth thermal annealing of [011]- ,[011(-)]-, and [010]-oriented quantum dot chains grown by molecular beam epitaxy on GaAs(100) substrates patterned by UV-nanoimprint lithography. We show that the quantum dot chains experience a blueshift of the photoluminescence energy, spectral narrowing, and a reduction of the intersubband energy separation during annealing. The photoluminescence blueshift is more rapid for the quantum dot chains than for self-assembled quantum dots that were used as a reference. Furthermore, we studied polarization resolved photoluminescence and observed that annealing reduces the intrinsic optical anisotropy of the quantum dot chains and the self-assembled quantum dots.     

Photoluminescence study of the nitrogen content effect on GaAs/GaAs1 − xNx/GaAs/AlGaAs: (Si) quantum well

We study the effect of nitrogen content in modulation-doped GaAs/GaAs_1 − xN_x/GaAs/GaAlAs:(Si) quantum well using low-temperature photoluminescence spectroscopy. The samples were grown on GaAs (001) substrates by molecular-beam epitaxy with different nitrogen compositions. The variation of the nitrogen composition from 0.04% to 0.32% associated to the bi-dimensional electron gas gives a new interaction mode between the nitrogen localized states and the GaAs_1 − xN_x/GaAs energies levels. The red-shift observed in photoluminescence spectra as function of nitrogen content has been interpreted in the frame of the band anticrossing model.     

Rapid fabrication of nanoneedle arrays by ion sputtering

We report a novel method for rapidly fabricating ordered nanoneedles using an ion beam that cuts through the Fe/GaAs single thin layer or the Fe/MgO/Fe/GaAs multilayer producing a pillar pattern followed by raster-scanning normal to the patterned area. However, such ordered nanoneedles were not formed on the pure GaAs substrate surface without the thin Fe film coating, nor were nanoneedles formed on the GaAs substrate coated with a thin Cr epitaxial film, when this method was used. It has advantages over other methods, being simple, fast and well controlled for fabricating one-dimensional nanostructure arrays, leading to a range of applications such as high aspect ratio sharp tips for atomic force microscope/atom probes and consequent possible quantum confinement effects or arrays of nanostructures for field-optical/photoluminescence emission and data recording.     

Preparation and characterisation of Au/InGaP/GaAs Schottky barriers for radiation damage investigation

High quality Au/InGaP Schottky diodes have been prepared as efficient test structures for a study of the radiation hardness of InGaP as space solar cell material. A detailed characterisation of the metal–semiconductor barriers obtained on both n (free carrier concentration ranging from 3×l0¹⁵ to 1.2×l0¹⁸ cm⁻³) and p-type (3.5×10¹⁷ cm⁻³) InGaP epitaxial layers lattice matched to GaAs substrate has been performed using current–voltage, capacitance–voltage and internal photoemission techniques. Excellent electrical properties were found for low doped (ideality factor of 1.05–1.06, rectification ratio of about 10¹⁰ at 0.7 V, reverse current lower than 1×10⁻¹² A at −2 V) as well as heavily doped samples (rectification ratios of about 10⁵ at 0.6 V). The barrier height values calculated by the different techniques were compared and discussed. Deep level transient spectroscopy (DLTS) spectra obtained on unirradiated samples did not show detectable deep levels with the exception of the heaviest doped sample showing a weak peak associated to the DX centre. After electron irradiation at 9 MeV with doses ranging from 5×l0¹³ to 1.5×10¹⁵ e cm⁻² the samples exhibited a broad dominant peak (activation energy in the 0.90–0.93 eV range) whose intensity increased linearly with the absorbed dose. The broadening of the peak and the observed increase of the corresponding trap concentration with the doping level suggest that this peak could be associated to complexes due to the interaction of primary defects, created by high irradiation energy, with each others and with the shallow impurities.     

Site-controlled growth of InP/GaInP quantum dots on GaAs substrates

A technology platform for the epitaxial growth of site-controlled InP quantum dots (QDs) on GaAs substrates is presented. Nanoholes are patterned in a GaInP layer on a GaAs substrate by electron beam lithography and dry chemical etching, serving as QD nucleation centers. The effects of a thermal treatment on the structured surfaces for deoxidation are investigated in detail. By regrowth on these surfaces, accurate QD positioning is obtained for square array arrangements with lattice periods of 1.25?μm along with a high suppression of interstitial island formation. The optical properties of these red-emitting QDs (λ?～?670?nm) are investigated by means of ensemble- and micro-photoluminescence spectroscopy at cryogenic temperatures.     

The base contact recombination current and its effect on the current gain of surface-passivated InGaP/GaAs HBTs

In this study, the effect of the emitter-base contact spacing on the current gain of InGaP/GaAs HBTs has been described and the base contact recombination current has been experimentally studied. When devices were passivated by nitride, the current gain of InGaP/GaAs HBTs showed no variation with the perimeter to area ratio, which suggested that the surface recombination current of InGaP/GaAs HBTs was negligible, leading the base contact recombination current to affect the current gain. It was found that the base contact recombination current significantly degraded the current gain when the emitter-base contact spacing was reduced to below 0.5 μm. The diode equation was used to model the base contact recombination current, and an ideality factor of 1.76 was obtained.     

Cubic GaN layers grown by metalorganic chemical vapor deposition on GaN templates obtained by nitridation of GaAs

Cubic gallium nitride epitaxial layers were grown by metalorganic chemical vapor deposition on GaN templates obtained by nitridation of GaAs substrates. The GaN structure can be peeled off the GaAs substrate and it can be handled separately. X-ray diffraction, Raman and photoluminescence measurements show that the epitaxial layers are cubic and monocrystalline.     

Microstructural analysis of Pd/Pt/Au/Pd ohmic contacts to InGaP/GaAs

Microstructural evolution during the annealing of Pd/Pt/Au/Pd p-ohmic contacts (with and without a thin layer of Zn) to InGaP/GaAs HBTs has been studied using transmission electron microscopy (TEM). Metal layers were deposited by electron beam evaporation directly onto the InGaP emitter layer with the intention of consuming the InGaP during annealing to contact the heavily C-doped p-type GaAs (3×10¹⁹ cm⁻³) base layer below. Initial reaction between Pd and Pt and InGaP formed a five-component amorphous layer (Pd, Pt, In, Ga and P), which crystallized to (Pt_xPd_1−x)5(In_yGa_1−y)P (0≤x, y≤1) at the interface between Pt and the amorphous layer. Annealing at temperatures ≥415°C caused complete decomposition of the InGaP and partial decomposition of the GaAs base layer, producing a contact consisting of (Pt_xPd_1−x)5(In_yGa_1−y)P, PtAs₂ and PdGa. The attainment of low contact resistances did not depend on the presence of Zn. Minimum values of 0.10−0.12 Ω mm were achieved after annealing at 415–440°C for contacts both with and without Zn. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influences of crystallographic misorientation of GaAs substrateson misfit stresses and microhardness of InGaP epilayers

InGaP epilayers were grown on the on-axis cut, 2° off, 6° off, and 10° off GaAs substrates by organo–metallic vapor phase epitaxy, and the influences of crystallographic misorientation of the substrate on the structural properties such as lattice mismatch, elastic strain, lattice curvature, misfit stress, X-ray line-width, and microhardness of the epilayers were investigated in this study. The material characterizations were carried out by the TXRD (triple-axis X-ray diffractometer) and the nanoindenter. With an increase of the substrate misorientation angle (S.M.A.), the relative incorporation of Ga atoms on the substrate surface was found to increase. Also, with an increase of S.M.A., the X-ray line-width of the InGaP epilayer was reduced, indicating that the crystal quality of the epilayer could be improved if the misoriented substrates were used. The elastic accommodation of the strain-free lattice misfit was found to be more remarkable in the misoriented samples. It was demonstrated, for the first time that the microhardness of the InGaP epilayer decreased with an increase of S.M.A. This indicated that the variation of microhardness of the epilayer was related to the improvement of the elastic characteristics and atomic displacement induced by the misoriented substrate. The results obtained demonstrated that the elastic characteristics and the crystal quality of the InGaP epilayer were remarkably enhanced and the microhardness of the epilayer decreased when the misoriented substrates were employed.     

Directed self-assembly of quantum structures by nanomechanical stamping using probe tips

We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs(100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed.     

Indium Composition Dependence of the Size Uniformity of InGaAs Quantum Dots on (311)B GaAs Grown by Molecular Beam Epitaxy

1.IntroJuctionTheformationofcoherentthree-dimensional(3D)islandsinlatticemismatchedsystembytheStranski-Krastanov(S-K)growthmodehasrecentlyreceivedextensiveattention,becausethismethodseemstobeoneofpromisingpathsforthedamagefreeforma-tionofquantumdots(QDs)structuresontheepilayer,..fa..li~6].Thisgrowthmodeisstartedwithanini-tialtwodimensionallayerdepositedonthesubstratematerial.Afteradepositionthicknessforacriticallayerisachieved,threedimensionalhighlystraineddotstructuresbegintogrowcoherefltl…