Decomposition Of Triethylgallium Research Articles

Mass spectrometric study of β-Ga2O3 growth process by metalorganic vapor phase epitaxy

In metalorganic vapor phase epitaxy of β-Ga2O3 using triethylgallium (TEGa) and O2 as precursors and Ar as the carrier gas, the gases directly above the substrate were sampled and analyzed by time-of-flight mass spectrometry. TEGa was found to decompose at 400 °C–600 °C via β-hydrogen elimination reaction to generate gaseous Ga, hydrocarbons (C2H4, C2H2, C2H6), and H2. When β-Ga2O3 was grown at temperatures greater than 1000 °C and with input VI/III ratios greater than 100, the hydrocarbons and H2 were combusted and CO2 and H2O were generated. The C and H impurity concentrations measured by secondary-ion mass spectrometry in the β-Ga2O3(010) homoepitaxial layer grown under these conditions were less than their respective background levels. Thus, to grow β-Ga2O3 without C and H contamination, conditions that favor the complete combustion of hydrocarbons and H2 generated by the decomposition of TEGa should be used.

Selective Nucleation and Growth of Large Grain Polycrystalline GaAs

AbstractA method for depositing large grained polycrystalline GaAs on lattice mismatched substrates through controlled nucleation and selective growth is presented. The process was developed on Si wafers. Nucleation site formation began with nanolithography to create submicron holes in photoresist on Si. Ga metal was electrochemically deposited into the holes. Subsequent arsine anneals converted the gallium deposits into GaAs. Photoluminescence and electron diffraction verified conversion to GaAs. Metal-Organic Chemical Vapor Deposition (MOCVD) enlarged the seed crystals to coalescence without creating additional nucleation sites within the patterned field. Having successfully demonstrated the approach, subsequent work has been directed at lower cost, alternative ways to define initial nucleation sites, such as, microcontact lithography and direct decomposition of triethyl gallium to Ga metal in the MOCVD chamber.

Self-limiting growth of GaAs molecular layer epitaxy using triethyl-gallium (TEG) and AsH 3

The surface reaction mechanism of GaAs MLE using a triethyl-gallium (TEG)-AsH 3 system was studied by varying the sequence of gas injection of TEG and AsH 3. The decomposition of TEG was found to be enhanced on the Ga-terminated (0 0 1)-oriented GaAs surface. The average lifetime of AsH x ( x=0, 1, 2) formed by the AsH 3 supply was 8 s, and the lifetime of the ethyl group of the ethyl-gallium compound formed by the TEG supply was about 2 s. The gas supply sequence was chosen to be within the two lifetimes, and the self-limiting growth at the monolayer was achieved in the TEG pressure region of more than 5.3×10 −3 Pa at a temperature of 270°C.

Surface reaction of triethylgallium and triethylantimony on GaSb(100)-(1×3)

The decomposition of triethylgallium (TEGa) and triethylantimony (TESb) on GaSb(100)-(1×3) was studied using temperature programmed desorption (TPD), static secondary ion mass spectroscopy, low energy electron diffraction and X-ray photoelectron spectroscopy. TEGa readily decomposes on the surface below 150 K, while TESb does not dissociatively adsorb below 320 K. The reactive sticking coefficient of TEGa is several orders of magnitude higher than that of TESb. The main decomposition products in TPD following dissociative adsorption were ethylene, hydrogen and a small amount of ethyl radical for both TEGa and TESb. Homolysis and β-hydride elimination are believed to be the desorption pathways for ethyl ligand removal from the surface following chemisorption of both precursors. Surface Ga atoms are proposed as reactive sites for ethyl reaction following the decomposition of TEGa and TESb on GaSb(100).

Pendeo-epitaxial growth of gallium nitride on silicon substrates

Pendeo-epitaxy (PE)1 from raised, [0001] oriented GaN stripes covered with silicon nitride masks has been employed for the growth of coalesced films of GaN(0001) with markedly reduced densities of line and planar defects on Si(111)-based substrates. Each substrate contained previously deposited 3C-SiC(111) and AlN(0001) transition layers and a GaN seed layer from which the stripes were etched. The 3C-SiC transition layer eliminated chemical reactions between the Si and the NH3 and the Ga metal from the decomposition of triethylgallium. The 3C-SiC and the GaN seed layers, each 0.5 µm thick, were also used to minimize the cracking and warping of the GaN/SiC/silicon assembly caused primarily by the stresses generated on cooling due to the mismatches in the coefficients of thermal expansion. Tilting in the coalesced GaN epilayers of 0.2° was confined to areas of lateral overgrowth over the masks; no tilting was observed in the material suspended above the trenches. The strong, low-temperature PL band-edge peak at 3.456 eV with a FWHM of 17 meV was comparable to that observed in PE GaN films grown on AlN/6H-SiC(0001) substrates.

Threshold photoemission analysis of the surface reactions of triethylgallium and trimethylgallium on GaAs(100): A promising technique for kinetics studies

The decomposition of triethylgallium and trimethylgallium on a As-stabilized GaAs(100) surface has been analyzed by near threshold photoemission. For T⩽200 °C, the negative photocurrent change induced by adsorption of these electron acceptor molecules is directly related to the coverage. The adsorbed diethylgallium species decompose very rapidly above 240 °C to adsorbed Ga atoms, resulting in a positive photocurrent change due to the lower work function of a Ga surface. The activation energy and preexponential factor of this decomposition reaction were derived independently in the temperature range 200–240 °C from the time dependence of the photocurrent emitted from the surface upon exposure to triethylgallium at saturated coverage.

Direct evidence for the β-hydride elimination mechanism in the decomposition of triethylgallium on GaAs(100)

Decomposition of the surface ethyl group formed by dissociative adsorption of triethylgallium (TEGa) on GaAs(100) is investigated using temperature programmed desorption. Deuterium labeling indicates that decomposition of the surface ethyl group proceeds exclusively through a β-hydride elimination reaction mechanism without any scrambling between α- and β-hydrogens. For undeuterated TEGa (TEGa-d 0), the surface ethyl group decomposes and desorbs simultaneously as C 2H 4 and H 2 at 600 K. For perdeuterated TEGa (TEGa-d 15), the desorption of C 2D 4 and D 2 occurs at a slightly higher temperature (630 K). Partially deuterated TEGa (TEGa-d 6), with deuterium on the α-carbons, results in H 2 and C 2H 2D 2 as desorption products at 600 K. A kinetic isotope effect of 8 ± 5 kJ mol −1 for hydride versus deuteride transfer is determined, which is consistent with cleavage of the C βH bond in the transition state, and with tunneling.

Growth rate enhancement of III–V antimonides on high-index substrates in metalorganic molecular beam epitaxy

Metalorganic molecular beam epitaxy growth of GaSb, InSb and AlSb on ( N 1 1) high-index substrates is studied. The growth rates of antimonides on (1 0 0) substrates are generally low because the decomposition of group III species is suppressed by the excessively adsorbed antimony atoms on the surface, i.e. the site-blocking effect. However, in the growth of GaSb using triethylgallium (TEGa) and elemental antimony, growth rates are enhanced on (3 1 1), (4 1 1) and (5 1 1) substrates. This substrate orientation dependence is also observed in the InSb growth using trimethylindium (TMIn) at low substrate temperatures, although with increasing substrate temperature, the growth rate becomes independent of substrate orientation due to the complete thermal decomposition of TMIn. These results imply that the decomposition of TEGa and TMIn is enhanced at atomic steps consisting of (1 0 0) and (1 1 1) planes and that the growth on high-index substrates is effective for the low-temperature growth of GaSb and InSb. On the other hand, the growth rate of AlSb using trimethylamine alane (TMAAl) is independent of substrate orientation because of low-temperature (∼ 100°C) decomposition of TMAAl.

A comparative study of the adsorption and thermal decomposition of triethylgallium and trimethylgallium at GaAs(100) surfaces studied by electron energy loss spectroscopy

High resolution electron energy loss spectroscopy (HREELS) has been used to study the adsorption and thermal decomposition of triethylgallium (TEGa) and trimethylgallium (TMGa) at Ga-terminated GaAs(100) surfaces. HREEL spectra recorded for adsorption of TEGa at room temperature show that the dominant surface species is based on intact ethyl (C 2H 5) groups. The surface species, which is likely to be diethylgallium (DEGa), is stable up to 250°C. Heating to 400°C results in the complete decomposition of the molecule via the facile β-elimination mechanism. For TMGa adsorption, HREEL spectra indicate that the stable surface species at room temperature is based on intact methyl (CH 3) groups, and is likely to be a dimethylgallium (DMGa) species. Decomposition of this species occurs with increasing temperature and involves the loss of CH 3 groups from the surface. In contrast to the clean decomposition of TEGa, a surface methylene (CH 2) species is also identified for TMGa at elevated temperatures and suggests an additional decomposition pathway involving loss of hydrogen from adsorbed CH 3 groups. The presence of this stable species in the case of TMGa, and not TEGa, is a possible explanation for the high carbon incorporation levels found in GaAs grown by chemical beam epitaxy (CBE) from this precursor.

Interaction of water with clean and gallium precovered Fe(111) surfaces

The interaction of water with the clean Fe(111) surface and that surface modified by small coverages of Ga has been investigated. Both thermal energy atom scattering and Auger electron spectroscopy have been used to probe this interaction. Water adsorption occurs via a molecular precursor state on these surfaces, and a passivated overlayer is formed on the clean surface exposed to water at 423 K. Small amounts of Ga precoverage, from the decomposition of triethyl gallium, strongly affect the subsequent water adsorption. Preadsorbed gallium reduces the molecular water sticking coefficient and inhibits water dissociation. This effect is proportional to the Ga precoverage. Electron beam irradiation during Auger measurement also strongly affects the water adsorption on the clean and Ga modified surface, and this effect is discussed.

Metalorganic molecular beam epitaxy growth and etching of GaSb on flat and high-index surfaces using trisdimethylaminoantimony

Metalorganic molecular beam epitaxy growth and etching of GaSb using triethylgallium (TEGa), trisdimethylaminoantimony (TDMASb) and elemental antimony (Sb 4) on flat and high-index surfaces are investigated. A higher growth rate is obtained on the ( n11) surface ( n = 5, 4, 3) using TEGa and Sb 4, indicating that the incorporation efficiency of Ga atoms is enhanced on these surfaces. This is explained by taking into account the steps where the decomposition of TEGa is enhanced. When only TDMASb is supplied, GaSb surfaces are etched for all misoriented GaSb substrates studied. On the other hand, when TEGa is simultaneously supplied in addition to TDMASb, the surface reaction is changed from etching to growth on the n = 5, 4, 3 surfaces. This is because the growth of GaSb is increased more than the etching by TDMASb on these surfaces. 77 K photoluminescence spectra show a sharp band-to-band transition peak at about 804 meV with a full width at half maximum of less than 9 meV indicating good optical quality. Unintentionally doped GaSb epilayers show p-type conduction with a 77 K hole mobility of 820 cm 2/V s and a hole concentration as 1.2 × 10 16cm −3.

Chemical beam epitaxy and laser-modified chemical beam epitaxy of InGaAs using tris-dimethylaminoarsenic

The growth of InxGaj1−xAs (x = 0.13–0.25) on GaAs by chemical beam epitaxy (CBE) and laser-modified CBE using trimethylindium (TMIn), triethylgallium (TEGa), and tris-dimethylaminoarsenic (TDMAAs) has been studied. Reflection high-energy electron diffraction measurements were used to investigate the growth behavior of InGaAs at different conditions. X-ray rocking curve and lowtemperature photoluminescence (PL) measurements were used to characterize the InGaAs/GaAs pseudomorphic strained quantum well structures. Good InGaAs/GaAs interface and optical property were obtained by optimizing the growth condition. As determined by the x-ray simulation, laser irradiation during the InGaAs quantum well growth was found to enhance the InGaAs growth rate and reduce the indium composition in the substrate temperature range studied, 440–500°C, where good interfaces can be achieved. These changes, which are believed to be caused by laser-enhanced decomposition of TEGa and laser-enhanced desorption of TDMAAs, were found to depend on the laser power density as well. With laser irradiation, lateral variation of PL exciton peaks was observed, and the PL peaks became narrower.

In-situ RHEED observation on surface reactions in laser-triggered chemical beam epitaxy of GaP

The surface reaction triggered by pulsed laser irradiation in chemical beam epitaxy (CBE) for GaP growth using triethylgallium (TEGa) and PH 3 was investigated with reflection high-energy electron diffraction (RHEED). The intensity of RHEED showed an abrupt decrease on laser irradiation followed by gradual recovery. The RHEED intensity recovered faster with a higher PH 3 flow rate, which indicates that the intensity recovery is related with the surface reaction between Ga atoms generated by laser irradiation and P atoms. This result showed that the decomposition of TEGa by laser irradiation and the formation of GaP occur alternately under continuous supply of source gases.

In-situ reflection high-energy electron diffraction observation of laser-triggered GaP growth in chemical beam epitaxy

Surface reaction triggered by N 2 laser irradiation onto adsorbed triethylgallium (TEGa) and reaction with phosphorus in chemical beam epitaxy (CBE) was studied by growth experiment and intensity change of reflection high-energy electron diffraction (RHEED). The growth rate shows saturation with a high TEGa supply, which suggests that the adsorption of TEGa on a surface is saturated. The change of RHEED oscillation was different from that of a continuous reaction. The result showed that the decomposition of TEGa and formation of GaP occur alternately under continuous supply of TEGa and PH 3.

Laser-Modified Chemical Beam Epitaxy of InGaAs/GaAs Multiple Quantum Wells Using Tris-Dimethylaminoarsenic

AbstractWe report for the first time laser-modified chemical beam epitaxy (CBE) of InGaAs/GaAs multiple quantum well (MQW) structures using trimethylindium (TMIn), triethylgallium (TEGa), and tris-dimethylaminoarsenic (TDMAAs), a safer alternative to arsine. X-ray rocking curve (XRC) and low-temperature photoluminescence (PL) measurements were used to characterize the pseudomorphic strained quantum well structures. As determined by the X-ray simulation, laser irradiation during the InGaAs well growth was found to enhance the InGaAs growth rate and reduce the indium concentration in the substrate temperature range studied, 440-S00°C, where good interfaces can be achieved. We attribute these changes to laser-enhanced decomposition of TEGa and laser-enhanced desorption of TDMAAs. With laser irradiation, lateral variation of PL exciton peaks was observed, and the PL peaks became narrower.

Chemical Beam Epitaxy (CBE) and Laser-Enhanced CBE of GaAs Using Tris-Dimethylaminoarsenic

ABSTRACTIn this paper, we report chemical beam epitaxy (CBE) of GaAs, and for the first time, Arion laser-assisted CBE using triethylgallium (TEGa) and tris-dimethylaminoarsenic (TDMAAs), a safer alternative to arsine. Samples grown at substrate temperatures above 490° C show n-type conduction, while those grown at lower temperatures show p-type conduction. An unintentional doping concentration of n∼lx1016 cm-3 with an electron mobility of 5200 cm2/V.s at 300 K and 16000 cm2/V.s at 77 K have been achieved. These are the best results reported for GaAs grown with TDMAAs. Laser-assisted CBE of GaAs is studied in the substrate temperature range of 240-550°C. There are two different substrate-temperature regions for laser-enhanced growth, 265 to 340°C and 340 to 440°C, which are believed to be caused by different TEGa decomposition mechanisms. The laser-assisted growth with TDMAAs, compared to AS4 or AsH3, shows a wider range of growth enhancement at low substrate temperatures.

Reflection high-energy electron diffraction observation of surface reaction triggered by pulsed laser irradiation during GaP growth in chemical beam epitaxy

Surface reaction triggered by pulsed laser irradiation in chemical beam epitaxy (CBE) for GaP growth using triethylgallium (TEGa) and PH3 was studied with reflection high-energy electron diffraction (RHEED). The intensity of RHEED showed an abrupt decrease on the irradiating laser followed by gradual recovery, and this change of intensity was different from that in usual CBE growth. The intensity recovery had considerable dependence on the PH3 flow rate, which indicates that the intensity recovery is related to the surface reaction between Ga atoms generated by laser irradiation and P atoms. This result showed that the decomposition of TEGa by laser irradiation and the formation of GaP occur alternately under continuous supply of source gases.

Composition Change of Indium Oxide Film by Triethylgallium Irradiation Prepared for In Situ Selective Epitaxy Use

Selective epitaxy of GaAs was examined by the chemical beam epitaxy (CBE) technique on indium oxide masks. The indium oxide films were prepared in vacuum with an alternating supply of trimethylindium (TMIn) and H2O2. The irradiation of triethylgallium (TEGa) and AsH3 on the indium oxide films was performed to examine whether or not GaAs deposition takes place on the oxide films. After irradiation for 30 min above 450°C, drastic change in the chemical composition of the oxide films was observed. That is, indium atoms in the oxide films were replaced by gallium atoms. It was found that gallium atoms released on the oxide surfaces by TEGa decomposition promoted the sublimation of indium oxide through reduction. Two probable reactions are proposed for this sublimation process. The difference between indium oxide and gallium oxide in the suppression of TEGa decomposition is briefly discussed as well. The investigation shows that selective epitaxy of GaAs on the indium oxide masks can be achieved by the CBE technique using TEGa and AsH3, although the sublimation of the oxide limits the film thickness of epitaxial GaAs.

On the effect of arsine for the decomposition of triethylgallium during epitaxial growth of GaAs

We report on mass-spectrometric studies of the decomposition behavior of triethylgallium (TEG) with and without arsine in a vacuum chemical epitaxy chamber. The measurements were performed during TEG supply cycles between 420 and 540°C and were accompanied by reflectance difference observations. Concentrations of reaction products produced during TEG decomposition were found to depend strongly on the arsine input. Based on an analysis of the ratio of ethane to ethene desorption and considerations of reaction pathways, we conclude that in the absence of arsine the β-hybride elimination process is dominant whereas the presence of arsine favors the formation and desorption of ethane. Moreover, the presence of arsine influences the amount of desorption of the diethylgallium as well as of the monoethylgallium compound.

Nanometer-Scale Deposition of Ga on HF-Treated Si(111) Surfaces through the Decomposition of Triethylgallium by Scanning Tunneling Microscopy

Ga dots on a nanometer scale were deposited using a scanning tunneling microscope (STM) through the decomposition of triethylgallium (TEGa) adsorhed on HF-treated Si(111) surfaces. The deposition of Ga dots of 2-13 nm in diameter was achieved by applying a negative voltage pulse to the sample, while no deposition was observed when a positive voltage pulse was applied. The conditions for Ga deposition were systematically investigated by varying the gap conductance, pulse height and pulse width. A tentative model for the mechanism of Ga deposition is proposed, in which TEGa molecules are decomposed by the electric field betwecn the tip and the sample.