A genetic algorithm approach is used to fit orbital interaction energies of sp3s* tight-binding models for the nine binary compound semiconductors consistent of Ga, Al, In and As, P, Sb at room temperature. The new parameters are optimized to reproduce the bandstructure relevant to carrier transport in the lowest conduction band and the highest three valence bands. The accuracy of the other bands is sacrificed for the better reproduction of the effective masses in the bands of interest. Relevant band edges are reproduced to within a few meV and the effective masses deviate from the experimental values typically by less than 10%. 相似文献
A detailed experimental study of electron cyclotron resonance (CR) has been carried out at 4.2 K in three modulation-doped GaAs/Al0.3Ga0.7As multiple quantum well samples in fields up to 30 T. A strong avoided-level-crossing splitting of the CR energies due to resonant magnetopolaron effects is observed for all samples near the GaAs reststrahlen region. Resonant splittings in the region of AlAs-like interface phonon modes of the barriers are observed in two samples with narrower well width and smaller doping concentration. The interaction between electrons and the AlAs interface optical phonon modes has been calculated for our specific sample structures in the framework of the memory-function formalism. The calculated results are in good agreement with the experimental results, which confirms our assignment of the observed splitting near the AlAs-like phonon region is due to the resonant magnetopolaron interaction of electrons in the wells with AlAs-like interface phonons. 相似文献
GaAs and CdTe pixel detectors have been developed over the last few decades. The applications of these detectors include X- and gamma-ray detectors working at room temperature. Fundamental properties such as detection efficiency and noise are determined by the material properties of the sensor material. Different materials have been evaluated over the years in search of the best choice for different types of radiation. This article describes the properties of GaAs and CdTe materials for single photon processing pixel detectors using the Medipix electronics. 相似文献
Surface acoustic waves of micrometre wavelength travelling on a monocrystal give diffraction satellites around each Bragg peak in an X‐ray diffraction diagram. By using a four‐crystal monochromator, a secondary two‐crystal analyser and masks reducing the footprint to the part of the crystal containing the acoustic modulation, it is possible to observe these satellites on a GaAs (001) surface using a laboratory diffractometer. The finite extension of the satellite diffraction rods and of the crystal truncation rod perpendicular to the surface leads to geometrical correction factors when convoluted with the instrumental resolution function, which had previously been ignored. The calculation of these geometrical correction factors in the framework of the kinematic approximation allows the determination of the surface acoustic wave amplitude, and the study of its attenuation and its dependence on radiofrequency power and duty cycle. The ability to perform such determinations with a laboratory diffractometer should prove useful in optimizing surface acoustic waves, which are presently used in a broad range of condensed matter physics studies. 相似文献
In this study, GaAs metal–oxide–semiconductor (MOS) capacitors using Y‐incorporated TaON as gate dielectric have been investigated. Experimental results show that the sample with a Y/(Y + Ta) atomic ratio of 27.6% exhibits the best device characteristics: high k value (22.9), low interfacestate density (9.0 × 1011 cm–2 eV–1), small flatband voltage (1.05 V), small frequency dispersion and low gate leakage current (1.3 × 10–5A/cm2 at Vfb + 1 V). These merits should be attributed to the complementary properties of Y2O3 and Ta2O5:Y can effectively passivate the large amount of oxygen vacancies in Ta2O5, while the positively‐charged oxygen vacancies in Ta2O5 are capable of neutralizing the effects of the negative oxide charges in Y2O3. This work demonstrates that an appropriate doping of Y content in TaON gate dielectric can effectively improve the electrical performance for GaAs MOS devices.
Capacitance–voltage characteristic of the GaAs MOS capacitor with TaYON gate dielectric (Y content = 27.6%) proposed in this work with the cross sectional structure and dielectric surface morphology as insets. 相似文献
Photonic structures capable of enhancing the light-outcoupling efficiency of embedded epitaxial quantum dots (QDs) in a broad spectral range are attractive for the realization of bright sources of single photons and entangled photon pairs. In this work, a planar-multilayer antenna is experimentally demonstrated for GaAs QDs embedded in AlGaAs membranes. The antenna consists of a metal (Au or Ag) reflector and a semi-transparent metal (Ag) director, with a thin oxide layer (hafnium dioxide (HfO2) or aluminium oxide (Al2O3)) between metal and semiconductor layers. Simulations using the 3D finite-difference time-domain (FDTD) method indicate a maximal efficiency of 43% (for collection optics with a numerical aperture (NA) of 0.85), a wavelength-dependent Purcell factor ranging from ≈ 0.7 to ≈ 1.45, strong directional emission characteristics, as well as a broad bandwidth of ≈ 30 nm. In the experiment, we find a Purcell factor compatible with the simulation results, a maximum collection efficiency as high as ≈ 19% and an ultralow multiphoton emission probability of 0.006 ± 0.005. The planar geometry, its compatibility with post-growth tuning methods, facile fabrication, broad spectral bandwidth, and achieved performance make the presented structure competitive for solid-state sources of quantum light. 相似文献
