Semiconductor–metal transition in GaAs nanowires under high pressure

We investigate the structural phase transitions and electronic properties of GaAs nanowires under high pressure by using synchrotron x-ray diffraction and infrared reflectance spectroscopy methods up to 26.2 GPa at room temperature.The zinc-blende to orthorhombic phase transition was observed at around 20.0 GPa.In the same pressure range, pressureinduced metallization of GaAs nanowires was confirmed by infrared reflectance spectra.The metallization originates from the zinc-blende to orthorhombic phase transition.Decompression results demonstrated that the phase transition from zincblende to orthorhombic and the pressure-induced metallization are reversible.Compared to bulk materials, GaAs nanowires show larger bulk modulus and enhanced transition pressure due to the size effects and high surface energy.     

A GaAs–InGaAs optoelectronic switch with multiple operation states

An optoelectronic switch with both n- and p-type delta-doped (-doped) quantum wells was investigated. The -doped structures formed potential wells for the carrier accumulation and potential barriers for the carrier injection. Being possessed of -doped sheets with different doping levels, the potential barriers were sequentially collapsed to produce a double negative-differential-resistance (NDR) phenomenon in the current–voltage (I–V) characteristics of the device, due to the carrier accumulation in the potential wells. The device also showed an optical function related to the barrier heights controllable by incident light.     

Fano-like electron–phonon interference in δ-doping GaAs superlattices

The interaction between electron excitations and LO phonons is studied by Raman scattering inδ-doping GaAs superlattices. The Raman spectra measured close to the E₀ +  Δ₀resonance of GaAs present Fano-like coupling of the LO phonons with the quasicontinuum single-particle electron excitations. Due to the self-consistent origin of the electron-energy spectrum in δ-doping superlattices the resonance of the Fano interference was found to be strongly dependent on the electron density as well as the excitation energy.     

Thermally stimulated terahertz radiation of plasmon–phonon polaritons in GaAs

The thermally stimulated excitation of radiative modes of surface plasmon–phonon polaritons in GaAs followed by the high-power terahertz (THz) radiation selective emission is studied and experimentally observed. The selective high-power THz radiation emitters in the 7–8 and 10–15 THz frequency ranges based on the heated highly doped (n>5?10¹⁷ cm^?3) GaAs plates are proposed.     

Photo- and electroluminescence of nitrogen isoelectronic traps in GaAs1–xPx

The variation with temperature of the charge on the surface of NaCl single crystals has been measured directly by means of vibrating capacitor probe. The charge is negative at room temperature, in agreement with theory based on values of the free energy of vacancy formation, decreases with increase of temperature in two stages to a zero value at the isoelectric temperature, and then becomes positive. Values of isoelectric temperature obtained on surfaces are consistent with those obtained by experiments on charged dislocations, which suggests that surfaces could be used to obtain accurate values of the free energy of formation of cation and anion vacancies.     

BEEM studies on GaAs/AlxGa1–xAs quantum wire structures

Ballistic electron emission microscopy (BEEM) was used to study laterally patterned GaAs/Al_xGa_1–xAs heterostructures. The measurements were carried out at room temperature in air as well as in liquid helium. Wet chemically etched quantum wires were identified both in topographic and BEEM current imaging. We find that the BEEM current is enhanced if ballistic electronis are injected directly into the quantum wire. The subsurface Al_xGa_1–xAs barrier influences the collector current by determining the BEEM current threshold and by influencing the Fermi level pinning position.     

Enhanced absorption process in the thin active region of GaAs based p–i–n structure

The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, Ga As based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells,photodetectors, and other photoelectric devices.     

Effect of SiO2–metal–SiO2 plasmonic structures on InGaAs/GaAs quantum well intermixing

Dielectric–metal–dielectric sandwich structures have been fabricated on top of an InGaAs/GaAs single quantum well (QW) structure to enhance atomic interdiffusion across the QW interfaces at elevated temperature during rapid thermal annealing using a halogen lamp as the heating source. The QW intermixing enhancement is realized during rapid thermal annealing. By placing a properly designed SiO₂–Ag–SiO₂ structure on top of the QW sample, a blueshift in photoluminescence emission from 920 to 882 nm was observed, larger than that obtained in a SiO₂-capped QW annealed at the same condition. Finite-difference time-domain simulation and optical reflectance measurements showed that the enhanced QW intermixing is due to the plasmonic resonance-enhanced light absorption and suppressed light reflection from the SiO₂–Ag–SiO₂ structure.     

Proton radiation effect on GaAs/AlGaAs core–shell ensemble nanowires photo-detector

We demonstrate that the GaAs/AlGaAs nanowires(NWs) ensemble is fabricated into photo-detectors. Current–voltage(I–V) characteristics are measured on Ga As/Al Ga As core–shell ensemble NW photo-detectors at room-temperature before and after 1-MeV proton irradiation with fluences from 1.0 × 10~(13) cm~(-2) to 5.0 × 10~(14) cm~(-2). The degradation of photocurrent suggests that the point defects induced by proton radiation could cause both carrier lifetime and carrier mobility to decrease synchronously. Comparing with a GaAs quantum well, the degradations of light and dark current for the irradiated NWs photo-detector indicate that NWs material is a preferable potential candidate for space applications.     

Electroluminescent device based on AlxGa1−xAs–GaAs quantum well nanostructures

AlGaAs–GaAs based quantum well nanopillar arrays are fabricated by using the UV lithography and the chlorine based reactive ion etching. The nanostructure is fabricated so as to get the confinement of carriers within the i-GaAs quantum well layer of 9 nm thick sandwiched between two barrier layers of Al_0.33Ga_0.67As of 11 nm thick in order to induce the possible light emission from the quantum well region. The size of pillars is obtained from SEM analysis. The number of pillars available within the 1 m² mesa size is found to be around 400 having the pillar size between 10 and 50 nm. Electroluminesence (EL) is detected from the nanopillars when applying a forward bias voltage of 1.3 V and the emitted light is observed at around 830 nm.     

Atmospheric-pressure metal–organic vapor-phase epitaxy of GaAsBi alloys on high-index GaAs substrates

We investigated the growth characteristics and properties of GaAsBi layers grown by atmospheric-pressure metal–organic vapor-phase epitaxy on different GaAs substrate orientations. The surface morphology of GaAsBi alloys was investigated by means of scanning electron microscopy. The structural and optical properties of the alloys were examined using high-resolution X-ray diffraction (HRXRD) and photoreflectance spectroscopy, respectively. HRXRD results show that the GaAsBi growth rate was significantly lower on (1 1 5)A than on (0 0 1), (1 1 1)A and (1 1 4)A GaAs. The highest Bi content was obtained for GaAsBi layers grown on (1 1 5)A GaAs substrates.     

Excited states of donors bound toXvalleys in GaAs–AlAs type II structures

We calculate the binding energies of 2s donor states bound tovalleys in type II GaAs–AlAs quantum well structures using an anisotropic variational method which enables us to take into account the effective mass anisotropy and quantum confinement. For a comparative study, we use two sets of effective masses obtained from different measurements [B. Rheinländeret al., Phys. Stat. Sol. (b)49, K167 (1972) and M. Goiranet al., Physica B177, 465 (1992)].     

Admittance of metal–insulator–semiconductor structures based on graded-gap HgCdTe grown by molecular-beam epitaxy on GaAs substrates

Metal–insulator–semiconductor structures based on n-Hg_1−xCd_xTe (x = 0.19–0.25) were grown by molecular-beam epitaxy on the GaAs (0 1 3) substrates. Near-surface graded-gap layers with high CdTe content were formed on both sides of the epitaxial HgCdTe. Admittance of these structures was studied experimentally in a wide temperature range (8–150) K. It is shown that an increase in the composition of the working layer and a decrease in temperature lead to a decrease in the frequency of transition to high-frequency behavior of the capacitance–voltage characteristics. The differential resistance of space charge region in the strong inversion increases with the composition of the working layer and for x = 0.22 and 0.25, the differential resistance is limited by the Shockley-Read generation. The values of the differential resistance of space charge region at different frequencies and temperatures were found.     

Anomalous Hall Effect in GaAs–AlGaAs Quantum Wells Doped by Nonmagnetic Impurities near the Metal–Insulator Transition

Journal of Experimental and Theoretical Physics - We report on the results of experiments indicating the existence of the anomalous Hall effect associated with the ferromagnetic ordering of spins...     

Effect of the Radiation Power on the Modification of Oscillations of the Photocurrent in Single-Barrier p–i–n GaAs/AlAs/GaAs Heterostructures with InAs Quantum Dots

JETP Letters - The effect of the power of incident light radiation on the behavior of quantum oscillations of the photocurrent in single-barrier p–i–n GaAs/AlAs heterostructures with...     

GaAs皮秒光电开关

利用大功率激光器和半导体的光敏性,可得到幅度数千伏,具有皮秒级上升时间和小于2皮秒抖动的电脉冲,本文讨论了这种开关的原理及得到的实验结果。     

Substrate removal for improved performance of QWIP–LED devices grown on GaAs substrates

Pixelless infrared imaging can be accomplished by epitaxially integrating a light emitting diode (LED) with a quantum well infrared photodetector (QWIP) large area device. The device acts as an infrared image converter by detecting a mid-to-far infrared (M/FIR) signal using the QWIP and outputting a near-infrared (NIR) signal via the integrated LED. By removing the device substrate, the detector performance can be significantly improved. This paper describes a substrate removal process, which uses a combination of mechanical polishing and chemical selective wet-etch. The choice of a suitable optical adhesive and the control of carrier/device parallelism are the two most important factors determining the success of the process.     

The use of Abell–Tersoff potentials in atomistic simulations of InGaAsSb/GaAs

In this paper we show the use of an optimally parameterized empirical potential of the Abell–Tersoff type to study the strain energy of the quaternary alloy InGaAsSb. We use our results to compute modified segregation energies in an improved kinetic model of segregation for the combined effects of group III and V exchange processes during epitaxial growth and compare with experimental data from Scanning Tunnelling Microscopy.