MBE Growth Of GaAs Research Articles

MBE growth and properties of GaAs, AlGaAs and InAs nanowires on SiC/Si(111) hybrid substrate

The possibility of GaAs, AlGaAs and InAs nanowires MBE growth on a silicon substrate with a nanometer silicon carbide buffer layer has been demonstrated for the first time. Under the same experimental conditions (including the same composition) the diameter of the nanowires is smaller than diameter of nanowires grown on silicon substrate. Based on the photoluminescence and TEM analysis it was suggest that when AlGaAs/SiC/Si NWs are grown, a physical complex structure is formed.

MBE growth of GaAs and InAs nanowires using colloidal Ag nanoparticles

Ag colloidal nanoparticles were used as a catalyst for molecular beam epitaxy of GaAs and InAs nanowires on the Si(111) substrates. The scanning electron microscopy measurements revealed that nanowires obtained are uniform and have small size distribution.

Monte Carlo investigation of the MBE growth of GaAs on the surfaces with different crystallographic orientations

MBE growth of GaAs on the surfaces with different orientations is studied by kinetic Monte Carlo simulations. The model allows taking into account the most relevant processes and reconstructions on the surfaces. The simulations show that islands grown on the (111)A surface have a chaotic shape whereas those on the (001) and (110) surfaces have more ordered structure due to the features of the surface structure. The diffusion length of Ga adatoms is observed to be dependent on the growth rate and V/III flux ratio. This influence is stronger for the (111) and (110) surfaces demonstrating that diffusion is weaker on the (001) surface. However, the diffusion length reduces with increasing growth rate and As2/Ga flux ratio tending to become equal for all surfaces under consideration.

25aB10 GaAsのMBE成長におけるリエントラントなRHEED振動の機構(半導体エピ(1),第34回結晶成長国内会議)

25aB10 GaAsのMBE成長におけるリエントラントなRHEED振動の機構(半導体エピ(1),第34回結晶成長国内会議)

Effect of GaAs native oxide upon the surface morphology during GaAs MBE growth

The GaAs native oxide effect upon the surface morphology of the GaAs epitaxial layer was studied with taking into account the main growth parameters of MBE technology: substrate temperature, effective As4/Ga flux ratio and growth rate. The MBE modes of atomically smooth and rough surfaces and surfaces with Ga droplet array formation were determined. The possibility of the obtaining of GaAs nanowires via GaAs native oxide layer was shown.

Kinetic Monte Carlo simulation of GaAs(001) MBE growth considering the V/III flux ratio effect

The kinetic Monte Carlo method is used to study the initial stage of GaAs molecular beam epitaxial growth on the GaAs(001) surface via fluxes of Ga atoms and As tetramers. The developed algorithm allows efficient investigation of the effects of the V/III flux ratio upon the geometrical characteristics of islands in the temperature range at which the (2 × 4) reconstruction of GaAs(001) is exclusively observed. The island density increases with an increasing V/III flux ratio, whereas the average island size decreases. The temperature dependences of the island characteristics are observed to be stronger at a smaller V/III flux ratio because large arsenic fluxes compensate the enhanced desorption at high temperatures. The island size distribution is more uniform at small V/III flux ratios, while a higher concentration of small clusters is observed as the arsenic flux increases. The analysis of the island morphology and size distribution function suggests that an increase in the V/III flux ratio and a decrease in the substrate temperature have similar effects upon island characteristics, which are attributed to suppression of surface diffusion in both cases.

Study of the GaAs MBE growth on (6 3 1)-oriented substrates by Raman spectroscopy

GaAs layers were grown by MBE on (6 3 1)-oriented substrates under a variety of growth conditions. The structural properties of the samples were studied by atomic force microscopy and micro-Raman spectroscopy. Hillock structures were formed on the layers surface presenting an elongation towards the [ 5 ¯ , 9 , 3 ] direction, with dimensions and density that depend on the growth conditions. Raman spectra from the samples showed two peaks corresponding to transversal (TO)- and longitudinal (LO) optical phonons. According to the calculated dipole selection rules both TO and LO phonons are allowed for backscattering from a perfect GaAs(6 3 1) surface, but with the intensity of the TO phonon much larger than that of the LO phonon. This result was used to study the changes in the GaAs surface morphology as a function of growth time and growth temperature. By employing a relatively high growth temperature and a high As pressure a surface corrugation was formed which could be used for the synthesis of one-dimensional structures.

MBE growth and characterization of GaAs 1−xSb x epitaxial layers on Si (0 0 1) substrates

We investigated the growth of GaAs 1− x Sb x ( x=1.0, 0.82, 0.69, 0.44, 0.0) layers on Si (0 0 1) substrates using AlSb as a buffer layer. Epilayers were grown as a function of As beam equivalent pressure (BEP) under a constant Sb BEP, and they were then characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), and micro-Raman scattering analysis. We confirmed that GaAs 1− x Sb x layers have been successfully grown on Si substrates by introducing AlSb layers.

MBE Growth of GaAs on Si through Direct Ge Buffers

AbstractThe result of GaAs growth on Si using a thin Ge buffer layer (about 0.5μm thick) is presented in this paper. A two-step method with a high temperature anneal between two steps is used to grow the Ge buffer layer. Single phase GaAs is grown on Ge by controlling the growth temperature, substrate miscut and the prelayers. No APD defect is observed by the XTEM and the threading dislocation density of GaAs grown using this method is about 5˜10×107cm-2. The PL intensity of GaAs is 10× less on Si substrate than on GaAs substrates.

Surface dynamics during MBE growth of GaAs(001) monitored by in‐situ reflectance difference spectroscopy

We have used in-situ reflectance difference spectroscopy to observe changes in GaAs(001) surface reconstructions during homoepitaxy. With a constant As4 flux of 5 × 10−6 Torr and growth rates of 1.1 ML/s, the starting (2 × 4) surface exhibits a sudden decrease in the RD signal corresponding to a (3 × 1) reconstruction as simultaneously evidenced by RHEED observations. Furthermore, by varying Ga fluxes so as to control changes in surface reconstructions between c(4 × 4) and (2 × 4), we traced reproducible features that lead us to propose a possible physical origin based on strained islands, induced by surface reconstruction, in order to explain the experimental observations. This last assumption was tested by depositing some atomic layers of InGaAs on a (2 × 4) GaAs (001) where the change in strain is evident. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Absorbed As Overlayer on a GaAs Substrate by GaAs MBE Growth under High As pressure with RHEED

Absorbed As Overlayer on a GaAs Substrate by GaAs MBE Growth under High As pressure with RHEED

AS pressure dependence on Si doping of MBE growth of GaAS on (111)A Substrates with interruption growth

AS pressure dependence on Si doping of MBE growth of GaAS on (111)A Substrates with interruption growth

MBE growth and properties of 3d transition metal-doped GaAs

Heavy 3d transition metal impurity doping into GaAs has been studied by low temperature molecular beam epitaxy. Temperature dependence of conductivities on 3d transition metal impurity doped layers have been well fitted by σ xx=σ 0 exp (ε/k B T) 1/2 , suggesting that variable range hopping in impurity band with soft Coulomb gap is dominant. Super paramagnetic behavior observed in Cr-doped GaAs has been suggested for local ferromagnetic spin ordering, while both Fe- and Co-doped GaAs layers are paramagnetic in the temperature range from room temperature to 2 K.

Efficiency difference in Ga adatom incorporation in MBE growth of GaAs with As 2 and As 4 molecular beams

The surface diffusion length of Ga adatom incorporation under As 2 and As 4 mixture flux was measured using microprobe-RHEED intensity oscillations in molecular beam epitaxy. The incorporation diffusion length of Ga on the (0 0 1) surface towards the [1 1 0] orientation showed a strong dependence on the As 2/As 4 ratio in the incident beam from the cracker cell. In keeping the total number of As atoms in the beam constant, it was found that the incorporation diffusion length of Ga decreases with higher As 2/As 4 ratio. This shows that As 4 molecules are partly incorporated into the GaAs epi-layer by the dissociative reaction at Ga atoms, while As 2 is almost completely incorporated. According to the calculation for the diffusion length of Ga, a single As 4 molecule decomposes to produce one As 2 molecule which is incorporated into the growing layer, whereas another As 2 molecule is lost by desorption. On the other hand, almost all As 2 molecules are active and adsorbed. This means that As 2 molecules are incorporated into GaAs epi-layer more efficiently than As 4 molecules.

Ga desorption during MBE growth of GaAS under high As vapor pressure

Ga desorption during MBE growth of GaAS under high As vapor pressure

MBE growth of antiphase GaAs films using GaAs/Ge/GaAs heteroepitaxy

Semiconductor films with periodic crystal orientation modulation have nonlinear properties useful for optical wave-mixing devices. We have developed an all-epitaxial technique for preparing orientation-patterned GaAs templates by GaAs/Ge/GaAs epitaxy and have used these to grow laterally orientation-patterned films. We have investigated the effects of substrate misorientation, substrate temperature, and prelayer to find conditions which will allow controlled MBE growth of antiphase GaAs using thin Ge interlayers. After fabricating templates from these films using lithography and etching techniques, we have regrown GaAs films with antiphase crystal orientation modulation in the plane of the film. The template-induced antiphase boundaries were observed to propagate vertically under all conditions examined.

Low-temperature MBE growth of GaAs on magnetic metal substrates

We present the regrowth of GaAs(0 0 1) on magnetic MnGa films, which are themselves grown epitaxially on GaAs(0 0 1) substrates. The diffusion of Mn into the GaAs overlayer, caused by a strong reactivity between Mn and As, is suppressed successfully by reducing the growth temperature to 200°C. The quality of the GaAs layers is sufficient for the growth of epitaxial MnGa/GaAs/MnGa trilayers showing magnetic interlayer coupling.

Density-functional theory studies on microscopic processes of gaas growth

Results for the elementary processes of MBE growth of GaAs on the frequently used GaAs(001) substrate are reviewed. We propose a bottom-up approach, where a growth model is constructed from the results of density functional theory (DFT) calculations. The implications of such a model can be tested against the information from STM images. First, the stable surface reconstructions are reviewed. Under the most commonly used conditions for MBE growth, the arsenic-rich β2 (2 × 4) reconstruction, which contains As dimers as basic building blocks, is the most stable. Next, the adsorption and diffusion of Ga atoms and As molecules on this surface is described. The DFT calculations support the picture that adsorbed Ga atoms are quite stable against re-evaporation. Thus, their mobility determines the homogeneity of the growing layer. Incorporation of Ga atoms proceeds by splitting the As dimers. We propose a model where growth proceeds in two stages: filling of trenches in the β2 (2 × 4) reconstruction, followed by nucleation of islands on the surface regions where the trenches are filled. We demonstrate how clusters of incorporated Ga atoms act as nuclei for the process of trench filling. Concerning island formation, the role of step formation energies and attachment probabilities of mobile adatoms at steps is discussed. Knowledge of these is crucial for an understanding of island shapes. Ongoing research is aiming at understanding of the microscopic mechanisms giving rise to the transition between the step-flow mode and the island-nucleation mode of growth.

Electron energy loss spectroscopy during MBE growth

A new detector that integrates energy loss spectroscopy with a standard reflection high-energy electron diffraction (RHEED) detector is used to study MBE growth of GaAs and GaN in real time. The detector is fully compatible with standard MBE machines and does not require any modifications to the system. While maintaining a spatial resolution of better than 200 μm on the phosphorous screen, the energy resolution of the system is typically better than 2 eV. We find that at 20 keV primary beam energy, the energy spectrum is dominated by surface plasmon losses. The shape and phase of RHEED intensity oscillations is not affected by excluding the inelastically scattered electrons. The energy spectrum is sensitive to surface roughness, material composition and layer thickness, providing additional information about the surface during growth.

Electrical properties of lateral p - n junctions formed on patterned (110) GaAs substrates

We have successfully demonstrated the formation of lateral p - n junctions via single-step Si-doped GaAs MBE growth over patterned (110) GaAs substrates. Current - voltage measurements indicate that the quality of the p - n junctions is position dependent; those located at the lower facet-flat boundary displayed superior rectification properties compared with the upper facet-flat junctions. Analysis of the lower junction forward characteristics revealed two types of current transport, each dominant over separate voltage ranges. Under low applied voltage, electron tunnelling via mid-gap states is proposed as the main mechanism, while diffusion and generation - recombination currents appear to dominate the device characteristics at higher voltages. In contrast, only tunnelling conduction was seen in the forward characteristics of the upper junctions. These effects are interpreted as due to compensated incorporation of Si in the region of the junctions, resulting from strong Ga diffusion from the (110) plane to the (100) surface. Series resistance values for the upper and lower junctions are consistent with this model, as are the dependences on growth temperature.