Planes Of GaAs Research Articles

Investigation of the effect of substrate orientation on the structural, electrical and optical properties of n-type GaAs1−xBix layers grown by Molecular Beam Epitaxy

Current-Voltage (I-V), Capacitance-Voltage (C-V), Deep Level Transient Spectroscopy (DLTS), Laplace DLTS, Photoluminescence (PL) and Micro-Raman techniques have been employed to investigate the effect of the orientation of the substrates on the structural, electrically and optically active defects in dilute GaAs1−xBix epilayers structures having a Bi composition x = ~5.4%, grown by Molecular Beam Epitaxy (MBE) on (100) and (311)B GaAs planes. X-ray diffraction results revealed that the in-plane strain in the Ga(As,Bi) layer of the samples grown on (100)-oriented substrate (−0.0484) is significantly larger than that of the samples grown on (311)B-oriented substrate. The substrate orientation is found to have a noticeable impact on the Bi incorporation and the electrical properties of dilute GaAsBi Schottky diodes. The I-V characteristics showed that (100) Schottky diodes exhibited a larger ideality factor and higher barrier height compared with (311)B samples. The DLTS measurements showed that the number of electrically active traps were different for the two GaAs substrate orientations. In particular, three and two electron traps are detected in samples grown on (100) and (311)B GaAs substrates, respectively, with activation energies ranging from 0.12 to 0.41 eV. Additionally, one hole trap was observed only in sample grown on (100) substrates with activation energy 0.24 eV. The observed traps with small activation energies are attributed to Bi pair defects. The photoluminescence (PL) and Raman spectra have evidenced different compressive strain which affects considerably the optical properties. Furthermore, the PL spectra were also affected by different contributions of Bi- related traps which are different for different substrate orientation in agreement with DLTS results.

Anisotropy mechanical behavior of crystals based on gallium arsenide cleavage processing

In order to promote the cleavage technology of GaAs, this paper explored the influence of the crystallographic orientation of mechanical properties on the quality of cleavage plane. Systematic theoretical models of certain key mechanical properties were proposed, and the mechanism of crack formation along two different directions during the cleavage process was discussed. The indentation tests were used to evaluate the crack formation and indentation morphology. A series of cleavage experiments were carried out to investigate the influence of mechanical properties and crack formation on the cleavage process. The results show that the Young’s modulus, Poisson’s ratio and Vickers hardness in the (100) plane along the <110> directions are 121.26 GPa, 0.02 and 5.757 GPa, respectively, and the values along the <100> directions are 85.26 GPa, 0.31 and 6.091 GPa, respectively. Combining theoretical calculations and indentation test results, the average fracture toughness in the <100> directions is approximately 10.94% higher than that in the <110> directions. Meanwhile, scratching along the <110> directions helps reduce the damage width. The {110} plane is a favorable cleavage plane in GaAs. These findings indicate that cleaving along the directions with a low fracture toughness is much easier to obtain a smooth cleavage plane. In addition, this paper proposed a useable theoretical and experimental approach to calculate mechanical properties for obtaining high-quality cleavage planes that can be widely used in other semiconductor materials.

Fracture surface analysis and quantitative characterization of gallium arsenide III-V semiconductors using fractography

Gallium arsenide (GaAs) is used in the most demanding semiconductor applications, including in the medical, aerospace and communication industries, where significant mechanical stresses are experienced during operation. Mechanical stresses from thermal expansion and mechanical loading can result in the fracture of GaAs crystals, a leading cause of semiconductor device failure. Unfortunately, the underlying fracture mechanisms in GaAs III-V semiconductors are currently not well understood. In this manuscript, we present a quantitative approach to identify the main GaAs fractographic features and correlate these to a crystal’s original mechanical fracture strength. In addition, detailed fractographic analysis was used to estimate the crystal hackle constant (analogous to the mirror constant in isotropic media), AXH110〈221〉= 1.58 MPa√m on the {110} cleavage planes of GaAs. Finally, crystal stereography and analytical geometry was used to confirm that the fractographic features correspond to the intrinsic symmetries of single-crystal GaAs.

Nonpolar GaAs Nanowires Catalyzed by Cu5As2: Insights into As Layer Epitaxy.

Controlled synthesis of GaAs nanowires (NWs) with specific phases and orientations is important and challenging, which determines their electronic performances. Herein, single-crystalline GaAs NWs are successfully synthesized by using complementary metal-oxide semiconductor compatible Cu2O catalysts via chemical vapor deposition at an optimized temperature of 560 °C. In contrast to typically Au catalyzed GaAs NWs, the Cu2O catalyzed ones are found to grow along nonpolar orientations of zincblende <110> and <211> and wurtzite <1̅100> and <2̅110>. The Cu2O catalysts are found to change into orthorhombic Cu5As2 after the NW growth, which is also significantly distinguished from the Au–Ga catalyst alloy in the literature. The Cu5As2 alloy plays the epitaxy role in the nonpolar GaAs NW growth due to the lattice matching with the nonpolar planes of GaAs, which is verified by the atomic stack model. These nonpolar oriented GaAs NWs have minimized stacking faults, promising for the other semiconductor synthesis as well as electronic applications.

Investigation of the structural, optical and electrical properties of indium-doped TiO2 thin films grown by Pulsed Laser Deposition technique on low and high index GaAs planes

The properties of In-doped TiO2 grown by Pulsed Laser Deposition on (100) and (311)B GaAs substrates have been investigated. X-ray diffraction and photoluminescence results have shown that samples grown on (311)B GaAs planes have better crystallographic properties than those grown on (100). Both anatase and rutile phases were detected in samples with lower In-doping (In = 5 nm) while only rutile phase was observed for higher In-doped samples (In = 15 nm). Furthermore, In-doping adversely affected the electrical properties of samples grown on (100) substrates while it enhanced those of (311)B samples. Two shallow defects were detected in all samples except for (311)B sample (In = 15 nm) where three shallow defects were observed. The presence of more shallow defects in this sample is evidenced by a red-shift in the absorption spectrum. It was concluded that sample (311)B (In = 15 nm) is best among all other samples and makes it more suitable for solar cell applications.

The Effect on the Optical Absorption Coefficients due to the Positions in the Plane of Square GaAs / Al(GaAs) Quantum Well Wire under the Laser Field

The Effect on the Optical Absorption Coefficients due to the Positions in the Plane of Square GaAs / Al(GaAs) Quantum Well Wire under the Laser Field

Density Functional Theory Calculations Revealing Metal-like Band Structures and Work Function Variation for Ultrathin Gallium Arsenide (111) Surface Layers.

Density functional theory (DFT) calculations have been performed on tunable numbers of gallium arsenide (100), (110), and (111) planes for their electron density of states (DOS) plots and the corresponding band diagrams. The GaAs (100) and (110) planes show the same semiconducting band structure with tunable plane layers and a band gap of 1.35 eV around the Fermi level. In contrast, metal-like band structures are obtained with a continuous band structure around the Fermi level for 1, 2, 4, 5, 7, and 8 layers of GaAs (111) planes. For 3, 6, and 9 GaAs (111) planes, the same semiconducting band structure as seen in the (100) and (110) planes returns. The results suggest the GaAs {111} face should be more electrically conductive than its {100} and {110} faces, due to the merged conduction band and valence band. GaAs (100) and (110) planes give a fixed work function, but the (111) planes have variable work function values that are smaller than that obtained for the (100) and (110) planes. Furthermore, bond length, bond geometry, and frontier orbital electron number and energy distribution show notable differences between the metal-like and semiconducting plane cases, so the emergence of plane-dependent electronic properties have quantum mechanical origin at the orbital level. GaAs should possess similar facet-dependent electronic properties to those of Si and Ge.

Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application**Supported by the National Natural Science Foundation of China under Grant No 61275174, and the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20100162110068.

A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers, and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide (GaAs) plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0 THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of 56 nm, which is less than one-tenth resonance wavelength, and the absorption coefficients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.

Structural and optical properties of diluted magnetic $$\hbox {Ga}_{{1-x}}\hbox {Mn}_{{x}}$$ Ga 1 - x Mn x As–AlAs quantum wells grown on high-index GaAs planes

We report on the structural and optical properties of $$\hbox {Ga}_{{1-x}}\hbox {Mn}_{{x}}\hbox {As}$$ –AlAs quantum wells (QWs) with $$x = 0.1\%$$ grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates with orientations (100), (110), (311)B and (411)B. Atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL) techniques were used to investigate these QWs. AFM results have evidenced the formation of Mn-induced islands, which are randomly distributed on the surface. These islands tend to segregate for samples grown on (110) and (411)B planes, while no clear segregation was observed for samples grown on (100) and (311)B orientations. Results show that the PL line width increases with Mn segregation. XRD measurements were used to determine $$2\theta , d$$ and cell parameters.

Investigation in band structures of GaAs/Al x Ga1−x As nanostructures superlattices at high magnetic field and low temperatures

We have investigated in the band structures E(d 1), E(k z , k p ) and the effective mass m*/m 0, respectively, along the growth axis and in the plane of GaAs (d 1 = 19 nm)/Al0.3Ga0.7As (d 2 = 5 nm) superlattice, performed in the envelope function formalism. Our results show the effect of the well thickness d 1 and the temperature on the electronic structures of this superlattice. The latter has a direct band gap of 1.529 eV, and the corresponding cutoff wavelength indicates that it can be used as a near-infrared detector. The position of Fermi level, based on the magnetoresistance measurements of Smrcka et al. and Fermi–Dirac integral computation at 0.4 K, predicts that this sample exhibits n-type conductivity with a two-dimensional electron gas.

Comparison of the Chemical Passivation of GaAs, In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As, and InSb with 1-Eicosanethiol

Self-assembled 1-eicosanethiolate layers were deposited on the oxide-free (100) crystal planes of GaAs, In0.53Ga0.47As, and InSb to protect the surfaces. The layer prevented re-oxidation in air for 30 min on GaAs but only 8 min on In0.53Ga0.47As based on the O 1s x-ray photoelectron spectroscopy state. The layer protected InSb from reoxidation for only 4 min based on the O Auger state. Well-ordered monolayers formed on GaAs and In0.53Ga0.47As based on transmission Fourier transform infrared (FTIR) spectroscopy. A partially ordered layer was formed on InSb based on attenuated total reflection FTIR. The increased reoxidation rate of InGaAs and InSb is due to the larger lattice parameter of these surfaces and their In content, which forms weaker bonds to S, Ga, and Sb compared to Ga bonding to As and S.

Impact of the substrate orientation on the N incorporation in GaAsN: Theoretical and experimental investigations

The growth orientation dependence of N incorporation on traditional (100) and high-index GaAs (311)A/B planes has been investigated by the first principle calculation and experimental measurement. Due to the electronegativity and atomic radius differences between As and N atoms, the GaN bond is much shorter than the corresponding GaAs bond as N occupies As atom site. The optimization to energetically preferred construction leads to the inward moving of N atom, while the displacement extent of three surface models exhibits considerable differences. More importantly, the theoretical result reveals a lower formation energy of N doping for N@(311)B GaAs surface and a larger one for N@(311)A GaAs surface as compared with the traditional (100) GaAs plane. The first principle investigations thus suggest the enhanced N incorporation in (311)B GaAsN, which is in good accordance with the secondary ion mass spectrometry (SIMS) measurement results of GaAsN layers by chemical beam epitaxy (CBE).

New orientations in the stereographic triangle for self-assembled faceting

Energetically unstable crystalline surfaces, among their uses, can be templates for the growth of periodic arrays of one-dimensional (1D) nanoscale structures. However, few studies have explored self-assembled faceting on high-index (HI) planes inside the stereographic triangle, and extant studies have not produced any criteria for encouraging the formation of one-dimensional periodic arrays. In this Letter, by analyzing the MBE growth of homoepitaxial facets on (631)A GaAs, a HI plane inside the triangle, we present a criteria to produce highly uniform 1D periodic arrays on unexplored surfaces. These families of planes are those belonging to the lines connecting the energetically stable HI GaAs (11 5 2) plane with any of the (100), (110), and (111) planes at the corners of the stereographic triangle. This novel strategy can lead to new possibilities in self-assembling 1D structures and manipulating physical properties, which in turn may result in new HI- and 1D-based experiments and devices.

Effects of rapid thermal annealing on two-dimensional delocalized electronic states of the epitaxial N δ-doped layer in GaAs

We have conducted rapid thermal annealing (RTA) for improving the two-dimensional (2D) arrangement of electronic states in the epitaxial nitrogen (N) δ-doped layer in GaAs. RTA rearranged the N-pair configurations in the GaAs (001) plane and reduced the number of non-radiative recombination centers. Furthermore, a Landau shift, representing the 2D delocalized electronic states in the (001) plane, was observed at around zero magnetic field intensity in the Faraday configuration.

Uniaxial Magnetic Anisotropy in Amorphous CoFeB Films on Different Orientational GaAs Substrates

Since the magnetic anisotropy of ferromagnetic (FM) films on semiconductor substrates has promising application for spintronics, it has stimulated extensive studies in the last two decades [1]. Remarkably, amorphous FM alloy films also exhibit uniaxial magnetic anisotropy (UMA) in the film plane when deposited on semiconductor substrates, e.g. CoFeB/GaAs (001) [2]. Although several models, including ‘bond-orientational anisotropy’ (BOA) model [2, 3] and random anisotropy model [4], have been proposed to explain the origin of UMA, the underlying mechanism has remained unclear yet. Considering that different cleavage plane of GaAs may have different inter-facial interaction with CoFeB film, a systematic investigation has been performed on the in-plane magnetic anisotropy of the CoFeB films deposited on different orientational GaAs substrates. Co 56 Fe 24 B 20 (CoFeB) films were deposited respectively on GaAs (001), GaAs (110) and GaAs (111) substrates by d.c. magnetron sputtering at room temperature. Before film growth, the surface contamination and oxides on the GaAs substrate should be removed by a standard procedure similar to that described in Ref. [5]. The base pressure was lower than 8.0×10−6 Pa and the Ar pressure was kept at 0.3 Pa during film deposition. A Ta film with 2 nm was deposited as capping layer to prevent the CoFeB film from oxidation. The magnetic hysteresis (M-H) loops were measured by a SQUID-VSM (Quantum Design). The angular dependence of M-H loop was measured by a vector VSM (Microsense EV7), from which the magnetic moment parallel (M x ) and perpendicular (M y ) to the field direction can be recorded simultaneously. All the measurements were performed in the film plane at room temperature.

Surface Chemistry of III-V Semiconductors After Wet Etching with HCl and H2O2

The introduction of III-V semiconductors in MOSFET technology has been hindered by the lack of good quality III-V oxides. These oxides are a source of surface states at the band edges or within the band gap that are a detriment to electronic performance. The removal of these oxides is typically accomplished by immersion in acid or basic aqueous solutions. The continuous etching of the substrate is achieved by adding an oxidizing agent. After etching, a smooth oxide-free surface is desired. HCl and H2O2 mixtures have been used for the etching of III-V materials. In this work, we perform a comparative study of the etching of the (100) crystal plane of GaAs, InAs, InP, GaSb, and InSb. The selective etching of these materials was studied as a function of H2O2 concentration (0.0001-5 M) and at a fixed HCl concentration (0.01 M). The etching rate was determined by profilometry measurements made on wafers patterned with conventional photolithography. The chemical composition of the surfaces after etching was studied with X-ray photoelectron spectroscopy (XPS) and the final roughness was characterized with atomic force microscopy (AFM). The etching rate of GaAs and InAs (same group V atom) showed a volcano-shaped dependence on H2O2 concentration (0.01 to 1 M). A maximum etching rate was observed at 0.1 M with a value of 1.1±0.1 nm/s for GaAs and 0.9±0.3 nm/s for InAs. For 1 M H2O2, the etching rate decreased to 0.035±0.010 nm/s for GaAs and 0.26±0.13 nm/s for InAs. The etching rate of InP increased when the H2O2 concentration was changed from 0.01 to 0.1 M, and showed no significant increase for higher concentrations within the error of the measurements. The etching selectivity of GaAs to InP increased from about 55 at 0.01 M H2O2 to 137 at 0.1 M H2O2, and then decreased to 4 at 1 M H2O2. The etching rate of GaSb and InSb (same group V atom) increased linearly between 0.0001 and 0.001 M H2O2, but dropped significantly at higher concentrations. These substrates were visibly oxidized at high H2O2 concentrations and HCl etching was unable to keep up with the rate of oxidation. Substrates with the same group V atom exhibited similar etching trends in the range of H2O2 and HCl concentrations studied. This suggests that the removal of the group V atom is the rate limiting step in the etching of these materials. Temperature programmed desorption (TPD) of a GaAs sample after immersion in HCl showed that the surface was terminated by As-Cl bonds. These results along with the chemical composition of the samples after etching will be used to propose reaction mechanisms of III-V semiconductors in HCl and H2O2 mixtures.

Confinement in thickness-controlled GaAs polytype nanodots.

Polytype nanodots are arguably the simplest nanodots than can be made, but their technological control was, up to now, challenging. We have developed a technique to produce nanowires containing exactly one polytype nanodot in GaAs with thickness control. These nanodots have been investigated by photoluminescence, which has been cross-correlated with transmission electron microscopy. We find that short (4-20 nm) zincblende GaAs segments/dots in wurtzite GaAs confine electrons and that the inverse system confines holes. By varying the thickness of the nanodots we find strong quantum confinement effects which allows us to extract the effective mass of the carriers. The holes at the top of the valence band have an effective mass of approximately 0.45 m0 in wurtzite GaAs. The thinnest wurtzite nanodot corresponds to a twin plane in zincblende GaAs and gives efficient photoluminescence. It binds an exciton with a binding energy of roughly 50 meV, including central cell corrections.

Elastic Energy in Inas Quantum Dot-in-a-Well Structures

The photoluminescence (PL), its temperature dependence and X ray diffraction (XRD) have been studied in the symmetric In0.15Ga1-0.15As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), obtained with the variation of QD growth temperatures (470-535°C). The increase of QD growth temperatures is accompanied by the enlargement of QD lateral sizes (from 12 up to 28 nm) and by the shift non monotonically of PL peak positions. The fitting procedure has been applied on the base of Varshni analysis to the temperature dependences of PL peaks. The obtained Varshni parameters testify that in studied QD structures the process of In/Ga interdiffusion between QDs and capping/buffer layers takes place partially. However, this process cannot explain the difference in PL peak positions. The XRD study has revealed the high intensity peaks at 2Θ= 31.6-31.8o (Kα1, Kα2) that correspond to the X ray diffraction of the Kα1 and Kα2 lines of Cu source from the (200) crystal planes of cubic GaAs. It was shown that the XRD peak is the superposition of the diffraction from the GaAs substrate and GaAs layers of quantum wells. The position of diffraction peaks related to the cubic GaAs substrate coincides with the very well know XRD data for the bulk GaAs. It means that the elastic strain in the GaAs substrate has been relaxed. At the same time the peak positions of the (200) diffraction peaks in GaAs epitaxial layers shift to the high angles in comparison with the bulk GaAs, testifying the compression strain in GaAs epitaxial layers. The minimum of elastic strain is detected in the structure with QD grown at 510°C that manifests itself by the higher QD PL intensity and lower the PL peak energy.

Elastic Energy in Inas Quantum Dot-in-a-Well Structures

The photoluminescence (PL), its temperature dependence and X ray diffraction (XRD) have been studied in the symmetric In0.15Ga1-0.15As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), obtained with the variation of QD growth temperatures (470-535°C). The increase of QD growth temperatures is accompanied by the enlargement of QD lateral sizes (from 12 up to 28 nm) and by the shift non monotonically of PL peak positions. The fitting procedure has been applied on the base of Varshni analysis to the temperature dependences of PL peaks. The obtained Varshni parameters testify that in studied QD structures the process of In/Ga interdiffusion between QDs and capping/buffer layers takes place partially. However, this process cannot explain the difference in PL peak positions. The XRD study has revealed the high intensity peaks at 2Θ= 31.6-31.8o (Kα1, Kα2) that correspond to the X ray diffraction of the Kα1 and Kα2 lines of Cu source from the (200) crystal planes of cubic GaAs. It was shown that the XRD peak is the superposition of the diffraction from the GaAs substrate and GaAs layers of quantum wells. The position of diffraction peaks related to the cubic GaAs substrate coincides with the very well know XRD data for the bulk GaAs. It means that the elastic strain in the GaAs substrate has been relaxed. At the same time the peak positions of the (200) diffraction peaks in GaAs epitaxial layers shift to the high angles in comparison with the bulk GaAs, testifying the compression strain in GaAs epitaxial layers. The minimum of elastic strain is detected in the structure with QD grown at 510°C that manifests itself by the higher QD PL intensity and lower the PL peak energy.

Emission and strain in InGaAs/GaAs quantum wells with InAs quantum dots obtained at different temperatures

The photoluminescence (PL), its temperature dependence and X ray diffraction (XRD) have been studied in the symmetric In0.15Ga0.85As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), obtained with the variation of QD growth temperatures (470–535°C). The increase of QD growth temperatures is accompanied by the enlargement of QD lateral sizes (from 12 up to 28nm) and by the shift non monotonously of PL peak positions. The fitting procedure has been applied for the analysis of the temperature dependence of PL peaks. The obtained fitting parameters testify that in studied QD structures the process of In/Ga interdiffusion between QDs and capping/buffer layers takes place partially. However this process cannot explain the difference in PL peak positions.The XRD study has revealed the high intensity peaks which correspond to the diffraction of X ray line from the (200) crystal planes of cubic GaAs. It was shown that the XRD peak is the superposition of the diffraction from the GaAs substrate and GaAs layers of quantum wells. The position of diffraction peaks related to the cubic GaAs substrate coincides with the very well-known XRD data for the bulk GaAs. At the same time the (200) diffraction peaks in GaAs epitaxial layers shift to the high angles in comparison with the bulk GaAs, testifying the compression strain in GaAs epitaxial layers. The value of elastic strain has been estimated. The minimum of elastic strain is detected in the structure with QD grown at 510°C that manifests itself by the higher QD PL intensity and lower PL peak energy.