GaAs Structures Research Articles

Enhanced growth and properties of non-catalytic GaAs nanowires via Sb surfactant effects

We report the effects of antimony (Sb) surfactant on the growth and correlated structural and optical properties of non-catalytic GaAs nanowires (NW) grown by selective area epitaxy on silicon. Strong enhancements in the axial growth with very high aspect ratio up to 50 are observed by the addition of small traces of Sb (1%–2%), contrasting the commonly reported growth limiting behavior of Sb in GaAs(Sb) NWs. The Sb surfactant effect modifies the growth facet structure from a pyramidal-shaped growth front terminated by {1–1–0} planes to a flat (111)B growth plane, that is even further improved by the presence of Si co-dopants. Additional benefits are seen by the substantial change in microstructure, from a heavily defected layer stacking in Sb-free GaAs NWs to a twinned phase-pure zinc blende structure in Sb-mediated GaAs(Sb) NWs. We directly confirm the impact of the altered microstructure on the optical emission and carrier recombination dynamics via observation of long, few-ns carrier lifetimes in the GaAs(Sb) NWs using steady-state and time-resolved photoluminescence spectroscopy.

Frequency effect on electrical and dielectric performance of Au/n–GaAs structure with RF sputtering MoO3 interfacial layer

Frequency effect on electrical and dielectric performance of Au/n–GaAs structure with RF sputtering MoO3 interfacial layer

Structural and optical changes in GaAs irradiated with 100 keV and 2 MeV protons

To clarify the proton energy dependence of proton irradiation damage in GaAs materials, intrinsic and Si-doped GaAs were irradiated with 100 keV and 2 MeV protons at different fluences. The evolution of lattice defects and optical properties of GaAs were analyzed by Raman spectroscopy, x-ray diffraction (XRD) spectroscopy, and photoluminescence (PL) spectroscopy. The results of Raman and XRD results show that the structures of the intrinsic GaAs and Si-doped GaAs does not change much after proton irradiation, which exhibits excellent radiation resistance. At the same time, the Raman results also prove that the radiation resistance of structural stability of Si-doped GaAs is lower than that of the intrinsic GaAs. However, in contrast to the structural properties, the optical properties of intrinsic GaAs degrade severely after irradiation in the PL spectrum, indicating that the optical properties of Si-doped GaAs are more stable than intrinsic GaAs. This is due to the changes of the light-emitting mechanism for Si-doped GaAs. In addition, the Raman and PL results also confirm that the damage produced by protons at 100 keV is greater than 2 MeV, which is consistent with the SRIM simulation.

Deep level defects in GaAs gradual p-i-n junctions after neutron irradiation

The high-voltage p+–p0–i–n0–n+ structures based on epitaxial gradual GaAs p0–i–n0 junction grown in hydrogen or argon atmosphere have been studied by capacitance-voltage spectroscopy and deep-level transient spectroscopy, DLTS, before and after neutron irradiation. After neutron irradiation, the broad bands associated with electron emission from the states lying above midgap appear in DLTS spectra of both p0–i–n0 GaAs structures. It is assumed that the carrier emission mechanism in the neutron-irradiated GaAs is the same as that in amorphous materials.

Structural, electronic and optical properties of CdGeAs2 with hybrid density functional (HSE06)

We calculate the structural, electronic and optical properties of the CdGeAs2 with the HSE06 functional. The results show that the structural parameters and band gap calculated by the HSE06 functional mixed with 25% Hatree-Fock exchange are closer to the experimental data. Comparing the band structures of CdGeAs2 and GaAs, it is concluded that CdGeAs2 is a direct band gap semiconductor. Based on the Bader charge and the electronic localization function, the properties of bonding between different atoms are analyzed. In addition, we explain the main spectral characteristics with the electronic structure, it provides a theoretical basis for in-depth understanding of the optical properties of CdGeAs2, and guides significance for the further theoretical research and practical application of CdGeAs2 crystals.

Thermodynamic and optoelectronic properties of GaAs[formula omitted]M[formula omitted] (M [formula omitted] Fe,Cu) ternary compounds via first principles

The electronic structure, band structure and optical properties of compounds GaAs(1−x)Mx (M = Fe,Cu), for x=0.25, 0.75, and 1 are discussed via Full-potential linearized augmented plane wave calculations. An increase in absorption in the visible spectrum is observed for all compounds, which, however, is associated with an increasingly metallic character as the metal concentration increases, to the point that compound GaFe is an indirect degenerate semiconductor. The addition of Fe and Cu to the compound decreases its stability, as demonstrated by the formation enthalpies, which become progressively more positive as the content in As is decreased. The calculations were performed using both the PBE and PBEsol exchange correlation potentials and the TB-mBJ method was used to verify the band structure obtained.

Experimental Studies of Modification of the Characteristics of GaAs Structures with Schottky Contacts after Exposure to Fast Neutrons

Experimental Studies of Modification of the Characteristics of GaAs Structures with Schottky Contacts after Exposure to Fast Neutrons

Design of Grating Type GaAs Solar Absorber and Investigation of Its Photoelectric Characteristics

In recent years, as a renewable clean energy with many excellent characteristics, solar energy has been widely concerned. In this paper, we propose an ultra-broadband solar absorber based on metal tungsten and semiconductor GaAs structure. A multilayer metal semiconductor composite structure composed of W-Ti-GaAs three-layer films and GaAs gratings is proposed. The finite difference time domain method is used to simulate the performance of the proposed model. High efficiency surface plasmon resonance is excited by adjusting the geometric parameters, and the broadband absorption of up to 2,350 nm in 500–2850 nm is realized. The spectrum of the structure can be changed by adjusting the geometric parameters to meet different needs. The proposed absorber has good oblique incidence characteristics (0–60°) and high short-circuit current characteristics. The geometry of the absorber is clear, easy to manufacture, and has good photoelectric performance. It can realize solar energy collection, light heat conversion, high sensitive sensing and other functions.

Calculations of Energy Band Structure of GaAs, GaSb and GaP Crystals as a Function of Temperature Using the Semiempirical Tight Binding Method

In this paper, the band structure of gallium group of III-V semiconductor has been calculated with temperature, the semi-empirical tight binding method was used to calculate the band structure and the matrix elements were calculated for both models sp^3 and sp^3 s^*. A computer program in MATLAB was designed to calculate the energy eigenvalues for the wave vector points in the first Brillouin zone between high symmetry points to form energy bands. The effect of temperature on the energy band of these group of crystals has been studied by changing the values of the lattice constant under the influence of temperature according to the Pierron relation and thus calculating the change in the length of the bond with temperature, which in turn affects the change in the values of the elements of the Hamiltonian matrix. The energy gap and refractive index were calculated at points of high symmetry as a function of temperature. The results showed a decrease in the energy gap values of GaAs, GaSb and GaP crystals with increasing temperature. Then the experimental Varshni relation was used to calculate the change in the energy gap values of these crystals and the results obtained from current study were compared with the results of Panish and Bellani, where the results showed that a model sp^3 s^* gives better results than the model sp^3.As well as the calculations of the refractive index of these crystals using the Moss formula showed that the refractive index will gradually increase with increasing temperatures.

Effect of Barrier Contacts on Carrier Transport in Homogeneous GaAs Structures Doped with Deep Cr and EL2 Centers

Effect of Barrier Contacts on Carrier Transport in Homogeneous GaAs Structures Doped with Deep Cr and EL2 Centers

Pressure-induced metallic phase transition in gallium arsenide up to 24.3 GPa under hydrostatic conditions

A series of experiments of structural, vibrational and electrical transport characterization of gallium arsenide (GaAs) have been performed up to 24.3 GPa under hydrostatic conditions in a diamond anvil cell (DAC) in conjunction with in situ Raman scattering spectroscopy, electrical conductivity measurements, high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). Upon compression, a phase transition from the zinc-blende (zb) to the orthorhombic (Cmcm) structure of GaAs was observed at 12.2 GPa through the discontinuous variations of the Raman shifts, Raman full-width at half-maximum values and electrical conductivity. Furthermore, the results of variable temperature electrical conductivity experiments confirmed that the high-pressure phase (Cmcm) exhibited one obvious metallic behavior. Upon decompression, the Raman scattering results of the recovered sample under ambient conditions indicated that the phase transition was reversible under hydrostatic conditions. The reversibility of the phase transition was further verified by HRTEM and AFM images for the recovered sample.

Sub-100 nm high spatial frequency periodic structures driven by femtosecond laser induced desorption in GaAs

This paper presents a previously unreported mechanism for the formation of High Spatial Frequency Laser Induced Periodic Surface Structures (HSFL) in GaAs upon irradiation by femtosecond laser pulses (repetition rate = 1 kHz, τ = 150 fs, λ = 390 nm) that is driven by point defect diffusion, desorption of surface atoms, and roughening of the surface. The HSFL have trenches that are 100 nm deep, an average spatial period of 65 nm, and are completely below the original surface. Sub-100 nm periodicity with high depth to period aspect ratio has not been previously observed in GaAs. In the proposed mechanism, laser irradiation generates point defects that diffuse to the surface. Interstitials that reach the surface can be easily desorbed and the remaining vacancies coalesce into vacancy islands. This results in a rough surface, which can excite surface plasmon polaritons. Despite our observations of periodicity corresponding to SPPs, calculations done using the excited dielectric function indicate that SPPs should not be supported. This points to the need to incorporate the cumulative effects of laser irradiation in existing models. This paper also presents evidence that desorption can also occur during HSFL formation in GaAs when irradiated with 780 nm in vacuum. The HSFL have the similar spatial period as GaAs irradiated in air with 780 nm, but completely below the original surface.

Effect of the AlGaAs Seed Layer Composition on Antiphase Domains Formation in (Al)GaAs Structures Grown by Vapor-Phase Epitaxy on Ge/Si(100) Substrates

Effect of the AlGaAs Seed Layer Composition on Antiphase Domains Formation in (Al)GaAs Structures Grown by Vapor-Phase Epitaxy on Ge/Si(100) Substrates

Probing the spin structure of the fractional quantum Hall magnetoroton with polarized Raman scattering

Starting from the Luttinger model for the band structure of GaAs, we derive an effective theory that describes the coupling of the fractional quantum Hall (FQH) system with photons in resonant Raman scattering experiments. Our theory is applicable in the regime when the energy of the photons $\omega_0$ is close to the energy gap $E_G$, but $|\omega_0-E_G|$ is much larger than the energy scales of the quantum Hall problem. In the literature, it is often assumed that Raman scattering measures the dynamic structure factor $S(\omega,\mathbf{k})$ of the FQH. However, in this paper, we find that the light scattering spectrum measured in the experiments are proportional to the spectral densities of a pair of operators which we identified with the spin-2 components of the kinetic part of the stress tensor. In contrast with the dynamic structure factor, these spectral densities do not vanish in the long-wavelength limit $k\to0$. We show that Raman scattering with circularly polarized light can measure the spin of the magnetoroton excitation in the FQH system. We give an explicit expression for the kinetic stress tensor that works on any Landau level and which can be used for numerical calculations of the spectral densities that enter the Raman scattering amplitudes. We propose that Raman scattering provides a way to probe the bulk of the $\nu=5/2$ quantum Hall state to determine its nature.

Performance Analysis of Ferroelectric GAA MOSFET with Metal Grain Work Function Variability

This work represents a unique GAA MOSFET with metal work-function variations (WFVs) and ferroelectric material as dielectric. A random distribution of metal grain (TiN) with grain size varied from 7nm to 10 nm is studied extensively. The potential distribution is studied by pushing the size of the device into lower technology node. The proposed structure exhibits improved drain current with lower threshold voltage. Additionally, comparative analysis on drain current of proposed structure with dual material GAA MOSFET and junction less GAA MOSFET is carried out. Irrespective of the type of the device and material used, the proposed device exhibits lower subthreshold swing (< 60 mV/decade), improved switching ratio (IOn/IOff) due to amalgam of ferroelectric and GAA structure.

Defect and Impurity-Complex Depassivation During Electron-Beam Irradiation of GaAs

Significant increases in thermal generation rates in molecular-beam epitaxy (MBE)-grown p-i-n-i-p GaAs structures are attributed to depassivation of hydrogen-defect/impurity complexes during high-intensity, low-energy electron-beam irradiation. Quantum calculations of relevant defect energy levels and reaction pathways suggest that depassivation of oxygen impurities is the likely cause of the observed degradation. Electric-field and excess-carrier-induced dehydrogenation of O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">As</sub> -H complexes is identified as a likely rate-limiting process, leading to the observed enhanced thermal carrier generation in these structures.

TCAD Temperature Analysis of Gate Stack Gate All Around (GS-GAA) FinFET for Improved RF and Wireless Performance

In this article, we investigated the impact of temperature variation on DC, analog, RF, and wireless performance of Gate Stack Gate All Around (GS-GAA) FinFET using SILVACO Atlas 3D simulator. The GAA structure introduction enhances the switching ratio (Ion/Ioff) by ∼152.37% and reduces the subthreshold swing (SS) by ∼6.5%. At gate voltage (Vgs) ∼ 0.725 V, the GS-GAA FinFET device exhibits the ZTC (Zero-Temperature-Coefficient) bias point, i.e., the effect of temperature on drain current gets nullified. DC parameters such as leakage current (Ioff), on current (Ion), SS, and threshold voltage (Vth) deteriorate with the rise in temperature. The enhancement in temperature degrades the RF and analog performance of the device by suppressing the parameters like transconductance (gm), device efficiency (TGF), cut-off frequency (fT), gain frequency product (GFP), gain-bandwidth product (GBP), etc. The device’s wireless performance is analyzed using linearity and harmonic distortion parameters such as gm3, gm2, 1-dB compression point, IIP3, VIP3, VIP2, IMD3, HD3, and HD2, and it shows significant improvement as the temperature increases from 300 K to 500 K.

A Comprehensive Study of Radiation Defect Clusters in GaAs Structures after Neutron Irradiation

A Comprehensive Study of Radiation Defect Clusters in GaAs Structures after Neutron Irradiation

The temperature dependent negative dielectric constant phenomena of Au/n–GaAs structure with CZO interfacial layer

In this study, the copper-doped (wt 3%) ZnO (CZO) thin film was deposited on n–type (100)–oriented GaAs substrate with the RF sputtering system and this film was annealed at 600 °C. The dielectric parameters such as dielectric constant ( $${\varepsilon }^{{\prime}}$$ ), dielectric loss ( $$\varepsilon^{ \prime \prime}$$ ), dielectric loss tangent ( $$\mathrm{tan}\delta $$ ), real ( $${M}^{{\prime}}$$ ) and the imaginary ( $$M^{\prime \prime}$$ ) part of the electric modulus, and ac conductivity ( $${\sigma }_{ac}$$ ) of Au/n–GaAs MOS structure with CZO thin film were examined in the temperature range of 200–380 K by 30 K steps. The variations of these parameters depending on the voltage were also discussed in the range of 1.5 V to 3.0 V by step 0.5 V. Dielectric constant has been studied in detail in three different temperature ranges as low (200 – 260 K), medium (290 K), and high (300 – 380 K). While the dielectric constant takes positive values for the low and medium temperature range in the forward bias voltage region, it takes negative values for the high temperature region. As a result of this study, negative dielectric constant behavior was observed for high temperature values.

Diagnostics of semiconductor structures by electrochemical capacitance-voltage profiling technique

The properties of interfaces in the heterostructures which frequently govern their operation are of particular importance for the devices containing heterostructures as active elements. Any further improving of the characteristics of semiconductor devices is impossible without a detail analysis of the processes occurring at the interfaces of heterojunctions. At the same time, the results largely depend on the purity of the starting materials and the technology of layer manufacturing. Moreover, the requirements to the composition and distribution of the impurity steadily get stringent. Therefore, the requirements regarding the methods of the impurity control and carrier distribution also become tougher both in the stage of laboratory development of the structure and in various stages of manufacturing of semiconductor devices. Electrochemical capacitance-voltage profiling is distinguished among the methods of electrical diagnostics of semiconductors by the absence of special preparation of the structures and deposition of the contacts to perform measurements, thus providing for gaining information not only about the impurity distribution but also about the distribution of free carriers. The goal of this work is to perform precise measurements of the profiles of free carrier distribution in semiconductor structures of different types, and demonstrate the measuring capabilities of a modern technique for concentration distribution diagnostics, i.e., electrochemical capacitance-voltage profiling. The method allows verification of the layer thickness in semiconductor heterostructures and provide a useful and informative feedback to technologists. To increase the resolution of the method and broad up the range of available test frequencies, a standard electrochemical profiler has been modified. Mapping data for GaAs substrate structure, the profiles of the concentration distribution of the majority charge carriers in SiC structures, GaAs structure with a p – n junction, pHEMT heterostructure, GaN heterostructure with multiple quantum wells, and in a silicon-based solar cell heterostructure are presented. The obtained results can be used to analyze the physical properties and phenomena in semiconductor devices with quantum-sized layers, as well as to improve and refine the parameters of existing electronic devices.