Influence of Substrate Misorientation on the Composition and the Structural and Photoluminescence Properties of Epitaxial Layers Grown on GaAs(100)

The influence of the degree of misorientation and treatment of a GaAs substrate on the structural and optical characteristics of homoepitaxial GaAs/GaAs(100) structures grown by metal–organic chemicalvapor deposition is studied. From the data obtained by a series of structural and spectroscopic techniques, it is shown that the degree of deviation of the substrate from the exact orientation towards the [110] direction by an angle of up to 4° brings about stepwise growth of the GaAs film in the initial stage and a further increase in the degree of misorienration towards the [110] direction to 10° results in an increase in the number of structural defects in the epitaxial film. At the same time, the samples of homoepitaxial structures grown by metal–organic chemical-vapor deposition on GaAs(100) substrates misoriented by 4° towards the [110] direction possess the highest photoluminescence efficiency; it is ~15% higher than the corresponding quantity for structures grown on precisely oriented GaAs(100) substrates. Preliminary polishing of the GaAs substrate (removal of an oxide layer) also yields the intensification of photoluminescence emission compared to emission in the case of an unpolished substrate of the same type. For samples grown on substrates misoriented by 4°, such an increase in the photoluminescence efficiency is ~30%.     

In0．2Ga0．8As-GaAs复合应力缓冲层上的1.3μm InAs／GaAs自组织量子点

用光荧光谱和原子力显微镜测试技术系统研究了在2 nm In0.2Ga0.8As和x ML GaAs的复合应力缓冲层上生长的InAs/GaAs自组织量子点的发光特性和表面形貌.采用In0.2Ga0.8As与薄层GaAs复合的应力缓冲层,由于减少了晶格失配度致使量子点密度从约1.7×109 cm-2显著增加到约3.8×109cm-2.同时,复合层也有利于提高量子点中In的组份,使量子点的高宽比增加,促进量子点发光峰红移.对于x=10 ML的样品室温下基态发光峰达到1350 nm.     

Relation between the Relaxation of Intrinsic Stimulated Picosecond Emission from GaAs with a Characteristic Charge-Carrier Cooling Time

Semiconductors - During the powerful picosecond optical pumping of a thin (~1 μm) GaAs layer, a stimulated intense (up to 1 GW/cm2) picosecond emission arises. It is found that the...     

Possibility of coherent light emission from Bose condensed statesin quantum-well systems

The possibility of coherent light emission in systems with a pairing of electrons and holes in a double quantum well spatially separated by a thin barrier [separated electron hole pairs (SEHPs)] is predicted. Bose condensation of excitons formed from SEHPs in GaAs/Al _xGa_(1-x)As double quantum wells of ~10 Å size are possible at relatively high temperatures. Coherent recombination emission due to the transfer of coherence from the Bose-condensed SEHPs to the photon field is expected     

Pixelless thermal imaging with integrated quantum-well infraredphotodetector and light-emitting diode

A large pixelless thermal imager based on the epitaxial integration of a GaAs-AlGaAs quantum-well infrared photodetector and a GaAs light-emitting diode is demonstrated. The device transforms a mid-infrared (9 μm) scene to a near-infrared (0.82 μm) emission image with a temperature resolution of ~1 K, limited by the integration capacity of the near-visible camera     

Terahertz Emission from GaAs Films on Si(100) and Si(111) Substrates Grown by Molecular Beam Epitaxy

We report on the terahertz emission from femtosecond-laser-irradiated GaAs layers grown on Si(100) and Si(111) substrates. The results show that the terahertz emission from GaAs on Si is stronger than that of a semi-insulating bulk GaAs crystal. This increase is attributed to the strain field at the GaAs/Si interface. In the GaAs of the Si(100) sample, the stronger terahertz emission is observed compared with GaAs on Si(111). Moreover, the effect of changing the doping type of the Si substrate from n-type to semi-insulating was also studied and it was found that the terahertz emission intensity of GaAs on semi-insulating Si(100) is stronger than that of GaAs on n-type Si(100). Finally, strong terahertz emission from GaAs on semi-insulating Si(100) was observed not only in the reflection geometry but also in the transmission geometry. These results hold promise for new applications of terahertz optoelectronics.     

Trap studies in GaInP/GaAs and AlGaAs/GaAs HEMT's by means oflow-frequency noise and transconductance dispersion characterizations

The presence of traps in GaInP/GaAs and AlGaAs/GaAs HEMT's was investigated by means of low frequency noise and frequency dispersion measurements. Low frequency noise measurements showed two deep traps (E _a1=0.58 eV, E_a2=0.27 eV) in AlGaAs/GaAs HEMT's. One of them (E_a2) is responsible for the channel current collapse at low temperature. A deep trap (E_a1'=0.52 eV) was observed in GaInP/GaAs HEMT's only at a much higher temperature (~350 K). These devices showed a transconductance dispersion of ~16% at 300 K which reduced to only ~2% at 200 K. The dispersion characteristics of AlGaAs/GaAs HEMT's were very similar at 300 K (~12%) but degraded at 200 K (~20%). The low frequency noise and the transconductance dispersion are enhanced at certain temperatures corresponding to trap level crossing by the Fermi-level. The transition frequency of 1/f noise is estimated at 180 MHz for GaInP/GaAs HEMT's and resembles that of AlGaAs/GaAs devices     

Structural and optical properties of InAs quantum dots in AlGaAs matrix

Structural and optical properties of InAs quantum dots (QDs) grown in a wide-bandgap Al_0.3Ga_0.7As matrix is studied. It is shown that a high temperature stability of optical properties can be achieved owing to deep localization of carriers in a matrix whose band gap is wider than that in GaAs. Specific features of QD formation were studied for different amounts of deposited InAs. A steady red shift of the QD emission peak as far as ∼1.18 μm with the effective thickness of InAs in Al_0.3Ga_0.7As increasing was observed at room temperature. This made it possible to achieve a much higher energy of exciton localization than for QDs in a GaAs matrix. To obtain the maximum localization energy, the QD sheet was overgrown with an InGaAs layer. The possibility of reaching the emission wavelength of ~1.3 μm is demonstrated. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 5, 2003, pp. 578–582. Original Russian Text Copyright ? 2003 by Sizov, Samsonenko, Tsyrlin, Polyakov, Egorov, Tonkikh, Zhukov, Mikhrin, Vasil’ev, Musikhin, Tsatsul’nikov, Ustinov, Ledentsov.     

Light emission as an analysis tool for GaAs ICs

As GaAs IC integration continues, device characterization and failure analysis get more difficult to perform. Standard visual and electrical inspections are becoming less adequate to evaluate devices and determine root cause of failures. A relatively new technique, used for several years on silicon devices, is light emission microscopy. The properties of light emission on silicon devices have been known for several decades. The light-producing properties of GaAs, a direct bandgap material, make it a natural for light emission study. This overview is intended to discuss the methodology and results of GaAs MESFET light emission.     

溅射ZnO薄膜钝化GaAs表面性能的研究

为了改善GaAs(110)与自身 氧化物界面由于高表面态密度而引起的费米能级钉扎(pinning)问题 ,提出采用射频磁控溅射技 术在GaAs(110)衬底上沉积一定厚度 ZnO薄膜作为钝化层,并利用光 致发光(PL)光谱和X射线光电子能谱(XPS) 等方法对ZnO薄膜的光学特性及钝化性能进行表征。实验结果表明,经ZnO薄膜钝化后的 GaAs样品,其本征PL峰强度提高112.5%,杂质峰强度下降82.4%。XPS光谱分析表明,Ga和As原子的比值从1.47降低 到0.94,ZnO钝化层能 够抑制Ga和As的氧化物形成。因此,在GaAs表面沉积ZnO薄膜是一种可行的GaAs表面钝化 方法。     

GaAs planar-doped barrier vacuum microelectronic electron emitters

A novel vacuum microelectronic electron emitter has been demonstrated in GaAs by using a planar-doped-barrier (PDB) structure. Emitted electrons are collected in high vacuum by a tantalum anode placed ~1 mm away from the emitter surface. Surface passivation with (NH ₄)₂S_x followed by in situ heating in vacuum has been used to obtain an atomically clean surface. An emission current density of 0.42 A-cm^-2 and an efficiency of 0.3% have been obtained from a 60 μm×60 μm emission region with an anode bias of 100 V     

砷化镓表面自旋极化光电子发射

本文详细地介绍了在圆偏振光作用下,NEA GaAs表面发射目旋极化光电子的原理,及NEA GaAs表面的制备和装置。介绍了表面Cs-O激活的方法。在用此法激活的NEA GaAs(100)表面上可得到灵敏度为8A/mW,极化度约用35%以上的光电子束。发现清洁的GaAs表面覆盖以50%60%Cs单原子层时,光电子的发射出现第一个极大值,同时发现稳定的发射取决于铯吸附量。     

Electromagnetic radiation from hot carriers in FET-devices

We report on the emission of light from si MOS and GaAs MES devices. Processes involving band-to-band transitions and a Bremsstrahlung-continuum below the band-gap are shown to exist. Spatially nonuniform emission from the MESFETs is observed. The GaAs results are compared with Monte Carlo simulations.     

Efficient near IR photoluminescence from gallium nitride layers doped with arsenic

Photoluminescence in the 1.2–1.4 eV spectral range from GaN:As layers grown on (0001) Al₂O₃ substrates was observed and studied. The photoluminescence is attributed to radiative recombination in GaAs nanocrystallites, self-organized in the GaN matrix during growth. The photoluminescence intensity attains a maximum at a growth temperature of ～780°C, which is explained by the competition between several temperature-dependent processes that affect the formation of GaAs nanocrystallites. Sharp emission lines were observed at the high-energy edge of the photoluminescence band. These lines are caused by an emission of bound excitons in the GaAs nanocrystallites and by phonon replicas of the bound-exciton emission. The energies of the corresponding optical phonons are typical of GaAs. The photoluminescence-excitation spectra exhibit features related to resonantly excited free and bound excitons as well as to excitons formed simultaneously with the emission of optical phonons.     

Stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells,grown on GaAs and Ge/Si(001) substrates

We report the observation of stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells, grown on Si(001) substrates with the application of a relaxed Ge buffer layer. Stimulated emission is observed at 77 K under pulsed optical pumping at a wavelength of 1.11 μm, i.e., in the transparency range of bulk silicon. In similar InGaAs/GaAsSb/GaAs structures grown on GaAs substrates, room-temperature stimulated emission is observed at 1.17 μm. The results obtained are promising for integration of the structures into silicon-based optoelectronics.     

Epitaxial necking in GaAs grown on pre-pattemed Si substrates

We report a new method for the natural reduction of threading dislocations in GaAs on Si by growing on patterned Si substrates. We also explore other effects of patterning on dislocation formation during growth: stress relief near the mesa edges at high aspect ratios, and limited dislocation nucleation and propagation. Prior to growth, the Si substrates were processed to produce a plurality of mesas varying in width (5-170 μm) and geometry (circular, rectangular, and square mesas). After growth of the GaAs, the material was characterized with cathodoluminescence (CL) and secondary electron microscopy. For a GaAs growth temperature of 570° C and a thickness of 10 μm, the GaAs grown on the 40μ-wide Si mesas show a factor of 1.6 increase in luminescence intensity over the luminescence intensity from the unpatterned control area. Also, the emission wavelength from the smaller mesas is shifted to shorter wavelengths as compared to GaAs/GaAs and the unpatterned control area. The emission wavelength and CL intensity varies across the mesas; for 40 μm wide mesas, the emission wavelength is fairly constant across the mesa and the CL intensity decreases near the edges, whereas for larger mesas the emission wavelength decreases and the CL intensity increases at the mesa edges. For the 40 μm wide mesas, the integrated CL intensity is equal to that of a control GaAs/GaAs grown with the same doping level. No cracks were observed in the GaAs grown on the Si mesas, even though the thickness of the GaAs was 10 μ,m.     

Growth features and spectroscopic structure investigations of nanoprofiled AlN films formed on misoriented GaAs substrates

Nanostructured aluminum-nitride films are formed by reactive ion-plasma sputtering onto GaAs substrates with different orientations. The properties of the films are studied via structural analysis, atomic force microscopy, and infrared and visible–ultraviolet spectroscopy. The aluminum-nitride films can have a refractive index in the range of 1.6–4.0 at a wavelength of ~250 nm and an optical band gap of ~5 eV. It is shown that the morphology, surface composition, and optical characteristics of AlN/GaAs heterophase systems can be controlled using misoriented GaAs substrates.     

Observation of bistability in GaAs quantum-well vertical-cavitysurface-emitting lasers

Two different types of bistability in proton-implanted GaAs quantum-well (QW) vertical-cavity surface-emitting lasers (VCSELs) have been observed. The first type of bistability has a small hysteresis width (~50 μA) in the light versus current and voltage versus current characteristics. Light-induced large negative differential resistance, random fluctuations, and self-pulsations are observed at the switching point. The emission patterns show that the bistability occurs at a spatially localized area under the output facet that covers only a small fraction of the N1S-μm-diameter aperture. The bistability stems from spatially localized saturable absorption. The second type of bistability has a large hysteresis width (~1 μA) in the L-1 characteristics and is observed well above the threshold current. In this case, no observable bistable loop exists in the voltage versus current characteristics, and the bistability is associated with transverse mode-hopping     

Vertical integration of a GaAs/AlGaAs quantum-well laser and along-wavelength quantum-well infra-red photodetector

A short-wavelength (~0.8 μm) GaAs/AlGaAs graded-index separate-confinement heterostructure quantum-well laser has been monolithically integrated with a long-wavelength (~8 μm) GaAs/AlGaAs multiple-quantum-well infra-red photodetector on a semi-insulating GaAs substrate by molecular beam epitaxy. The vertical integration method is used and the combined structure is a pinin structure. Both the laser and detector exhibit excellent characteristics. At room temperature, the ridge waveguide laser has an extremely low threshold current of 25 mA and a differential quantum efficiency above 65% with a stripe width of 20 μm. The quantum-well detector has a peak response at 8 μm and a responsivity of 0.7 A/W     

Optical thyristor based on GaAs/InGaP materials

The possibility of creating thyristor structures with external optical control by laser radiation with a wavelength of ~800 nm, based on single-crystal wafers of semi-insulating GaAs and layers of InGaP with the lattice parameter compatible with GaAs, is shown.