Papers by Keyword: GaAs

Abstract: A theoretical study of the effect of applying a lateral electric field on type I and type II GaAs/AlGaAs quantum ring with different Al concentration in the barrier is presented. The effect on the quantum states of the carriers was investigated using the approximation of the effective mass. It’s showed that the electric field has a great effect on the wavefunction and the energy of the carriers. The transition point of the quantum ring from type I to type II was found with increasing electric field strength. For electric fields less than 4.75 x 10^-4 V/cm, the quantum ring is of type II: the symmetry of electron ground state is X. Above this threshold, it transitions to type I : the symmetry of electron ground state is Γ. Also, the effects of electric field on the linear and non-linear optical properties of the studied structure illuminated with different incident optical intensity were studied. There is an increase in the radiative lifetime with a notable decrease in the absorption coefficient and the refractive index with the increase in the intensity of the electric field. It’s noted that the increase in the type II quantum ring lifetime (20%) is greater than that of type I quantum ring (10 %) due to the confinement of the G-electron in the quantum ring which is not the case with the X-electron. To the best of our knowledge, this article is the first theoretical study of the influence of lateral electric field on physical properties of type II GaAs/AlGaAs quantum ring structures.

Abstract: The regular shape of a circular dielectric resonating antenna (DRA) is changed in this paper. The proposed dielectric resonator has a perturbed circular shape in which the least arc to arc distance is same as that of the wavelength (λ) that is calculated from the design frequency. The proposed structure has a substrate and a dielectric resonator which include dielectric materials. In this paper different dielectric materials have been used both for substrate as well as dielectric resonator and the performance of the proposed DRA has been evaluated in terms of S-Parameter ( <-10 dB) , antenna gain , radiation efficiency , directivity . The dielectric materials like FR4 epoxy and GaAs have been used for the substrate. For perturbed shaped dielectric resonator, the materials having high dielectric constant like silicon, alumina 92_pct.

Abstract: The results of the presented studies demonstrate the possibility of using two and three component solid solutions, based on elements of the A3B5 groups, as thin barrier layers to cover an array of structured InAs quantum dots for photoactive heterointerfaces of solar energy. When using three-component solid solutions for QD barrier layers, a decrease in the thermionic generation in the near infrared spectrum and a decrease in the dark current of the heterointerface are obtained.

Abstract: In this paper, natural heterogeneities of the potential on the degenerated semiconductor surface are discussed as well as the barrier height fluctuations in metal-semiconductor contacts. In the case of electroactive dopant linear screening, characteristic values of chaotic potential amplitudes have been defined. The dependence is shown of these heterogeneities on semiconductor electrophysical parameters.

Abstract: The process of GaAs and InAs substrates high-temperature annealing under the Langmuir evaporation conditions is studied by Monte Carlo simulation. The temperature range of gallium arsenide and indium arsenide congruent and incongruent evaporation are determined. It was demonstrated that the congruent evaporation temperature T_c is sensitive to the vicinal surface terrace width. The decrease of the terrace width results in a decrease in the congruent evaporation temperature. The Ga and In diffusion lengths along the (111)A and (111)B surfaces at congruent temperatures are estimated. The surface morphology transformation kinetic during high-temperature annealing is analyzed.

Abstract: The dependences of congruent evaporation temperature T_c and the desorption activation energies of GaAs components on the substrate surface orientation are analyzed using Monte Carlo simulation. On the vicinal surfaces with the (111)A orientation at temperatures exceeding T_c, the metal droplets start to grow at step edges, and, with the (111)B orientation, the droplets nucleate randomly on the terraces. The droplet concentration on the (111)B surface is higher than that on the (111)A surface. The droplet-crystal interface roughness is different for (111)A and (111)B orientations. The T_c of (111)B surfaces is lower than that of (111)A surfaces. For both surface orientations, T_c decreases when the vicinal surface terrace width is shorter than the double gallium diffusion length. The gallium and arsenic desorption activation energies dependence on the vicinal surface misorientation is demonstrated. A sharp increase in the arsenic desorption rate is observed with an increase of the (111)A surface coating with liquid gallium.

Abstract: In this study of nanoscale etching for state-of-the-art device technology the importance of the nature of the surface oxide, is demonstrated for two III-V materials. Etching kinetics for GaAs and InP in acidic solutions of hydrogen peroxide are strikingly different. GaAs etches much faster, while the dependence of the etch rate on the H⁺ concentration differs markedly for the two semiconductors. Surface analysis techniques provided information on the surface composition after etching: strongly non-stoichiometric porous (hydr)oxides on GaAs and a thin stoichiometric oxide that forms a blocking layer on InP. Reaction schemes are provided that allow one to understand the results, in particular the important difference in etch rate and the contrasting role of chloride in the dissolution of the two semiconductors.

Abstract: Photovoltage formation across Si and GaAs p-n junctions exposed to laser radiation is experimentally investigated. When the photon energy is lower than semiconductor forbidden energy gap, the photovoltage is found to consist of two components, U=U_f+ U_ph. The first one Uf is fast having polarity of thermoelectromotive force of hot carriers. The second one Uph is slow component of opposite polarity, and it is caused by electron-hole pair generation due to two-photon absorption. Uph was shown to decrease with the rise of radiation wavelength due to diminution of two-photon absorption coefficient with wavelength. Predominance of each separate component in the formation of the net photovoltage depends on both laser wavelength and intensity.

Abstract: In this paper, the defect generated in the interaction of gamma ray resulting from cesium ion (Cs-137) and GaAs as a main portion of gallium arsenide field effect transistor (GaAsFET) is simulated using SRIM (Stopping and Range of Ions in Matter). The induced defects are in the form of vacancies, defect clusters and dislocations. Besides, the defect is found influencing the kinetic processes that occur both inside and outside the cascade volume. The radiation tolerance between the conventional scale and nanoscale thickness of GaAs layer is also being compared. From the findings, it is observed that when the thickness of GaAs layer is scaled down, defect that induced by the energy deposition of gamma radiation is significantly lesser. This means that nanoscale GaAs layer features improved radiation robustness towards the deposition of energetic ions.

Abstract: The in-situ monitoring of the MBE grown nanostructures can be carried out using the RHEED method. During the droplet epitaxal growth, the observation of the nanostructure formation is very important to understand the growth kinetics. In the present work, a novel in-situ RHEED evaluation and further MBE related developments are introduced, with which the quality of the nanostructure preparation can be improved.