Carbon Incorporation In GaAs Research Articles

Incorporation efficiency of carbon in GaAs using carbon tetrabromide in solid source molecular beam epitaxy

The incorporation efficiency of carbon in GaAs using carbon tetrabromide (CBr4) was studied. A series of carbon-doped GaAs samples were grown at different CBr4 pressures and V/III ratios using solid source molecular beam epitaxy (SSMBE). The results showed a high carbon incorporation efficiency of ∼30% within the CBr4 pressure range up to 2×10−7 Torr, which resulted in carbon doping concentration of up to 2×1020 cm−3. However, an increase in V/III ratio was found to reduce the carbon incorporation efficiency. Based on our experimental results, a kinetic model was developed to explain the effect of carbon incorporation in GaAs from CBr4 in SSMBE growth. The model incorporates the effects of different CBr4 decomposition rates on the As-covered and Ga-covered surface.

Incorporation behaviour of carbon and silicon on (100) and (111) surfaces during growth of GaAs/GaAs and Ga 0.47In 0.53As/InP by molecular beam epitaxy

Silicon and carbontetrabromide were used as dopant sources in the growth of GaAs/GaAs and Ga 0.47In 0.53As/InP structures. We studied the incorporation behaviour of these group IV atoms on (100) and {111} surfaces as a function of growth temperature. The free carver concentrations determined by Hall measurements for Si-doped GaAs and Ga 0.47In 0.53As layers are independent of growth temperature on all surface orientations studied. Silicon acts fundamentally as a donor except, as expected, for doped layers on (111)A GaAs substrates, where it acts as an acceptor. Carbon incorporation in GaAs and Ga 0.47In 0.53As always results in a p-type conduction independent of the surface orientations (100)/{111} or the growth temperatures we used. In contrast to the results on GaAs, carbon shows a strong temperature-dependent activation in Ga 0.47In 0.53As grown on (100) and (111)B surfaces. Carbon-doped Ga 0.47In 0.53As on (111)A and carbon-doped GaAs layers on (100)/{111} GaAs surfaces exhibit only a very weak dependence of the carrier concentration on the growth temperature. A significant amphoteric behaviour of carbon was not observed in any of the materials investigated.

Optimization of carbon incorporation in GaAs during molecular beam epitaxial growth

Carbon-doped GaAs with dopant concentrations up to about 1020 cm−3 has been grown by molecular beam epitaxy. Above a critical carbon concentration, which depends on the deposition parameters, the surface deteriorates and loses its mirror-like appearance. From X-ray diffractometry and scanning electron microscopy, a diagram is established separating two areas with rough and mirror-like surface morphologies. The electrical properties as well as the morphology of GaAs : C can be simultaneously improved by a careful adjustment of the deposition parameters according to this diagram.

Optimization of carbon incorporation in GaAs during molecular beam epitaxial growth

Optimization of carbon incorporation in GaAs during molecular beam epitaxial growth

Low carbon incorporation in GaAs grown by chemical beam epitaxy using unprecracked arsine, trimethylgallium and triethylgallium

GaAs epilayers have been successfully grown by chemical beam epitaxy (CBE) using unprecracked arsine (AsH 3) with trimethylgallium (TMG) or triethylgallium (TEG). In the growth using AsH 3 and TMG, three different regions of growth rates were observed with respect to the growth temperature, which is similar to that observed in the conventional CBE or metalorganic molecular beam epitaxy (MOMBE). The growth rates by AsH 3 and TEG, however, produced an anomalous dependence on the growth temperature revealing two humps. Hall measurement, photoluminescence, and secondary ion mass spectrometry (SIMS) analysis data show that all films are p-type and the carbon concentration is greatly reduced compared to the epilayers grown by CBE which employs TMG and precracked arsine. It was also found that the uptake of carbon impurity is significantly reduced when TMG is replaced with TEG. Our results indicate that surface hydrogen atoms dissociated from arsine play an important role in removing hydrocarbon species from the growth surface.

Carbon incorporation in GaAs and AlxGa1−xAs layers grown by molecular-beam epitaxy

GaAs:C and AlxGa1−xAs:C films, grown by solid-source molecular-beam epitaxy with doping levels beyond 1019 cm−3, have been studied by high-resolution double-crystal x-ray diffraction, Hall-effect measurements, and secondary-ion-mass spectroscopy (SIMS). Comparison between x-ray diffraction and Hall-effect data indicate that carbon is preferentially incorporated as acceptor on As lattice sites both in the GaAs:C and in the AlxGa1−xAs:C films. It was found that the higher the AlAs mole fraction the higher is the concentration of carbon incorporated on As sites (CAs). Moreover, SIMS results showed that the total amount of carbon in the host lattices largely exceeds CAs. Our findings are explained by supposing that carbon atoms are incorporated on As sites and on interstitial sites. Furthermore, it is shown that the carbon interstitial concentration can be reduced growing at higher arsenic flux and higher substrate temperature in GaAs:C as well as in AlxGa1−xAs:C layers.

Effect of electron cyclotron resonance generated hydrogen plasmas on carbon incorporation and interfacial quality of GaAs and AlGaAs grown by metalorganic molecular-beam epitaxy

The authors have investigated the effect of in situ hydrogen plasmas generated by electron cyclotron resonance on growth rate and carbon incorporation in GaAs and AlGaAs grown by metalorganic molecular‐beam epitaxy using triethylgallium and trimethylamine alane. Carbon backgrounds in GaAs grown at 500 °C were found to increase with increasing microwave power over the range 100–200 W and also with increasing H2 flow at 175 W. Hydrogen plasmas did not significantly increase the growth rate for either GaAs or AlGaAs even at growth temperatures as low as 375 °C. As at higher temperatures, carbon levels were not reduced in GaAs grown at low temperatures though some improvement was observed for AlGaAs grown at 375 °C. Plasmas were found to be much more effective for cleaning substrates prior to growth. At 500 °C, low microwave powers and moderate exposure times were found to produce the lowest levels of interfacial C, O, and Si contamination.

Carbon Incorporation in Gaas grown by UHVCVD Using Trimethylgallium and Arsine

ABSTRACTWe present results of a study on the effect of unprecracked arsine(AsH3) and trimethylgallium(TMGa) on carbon incorporation in UHVCVD(Ultra High Vacuum Chemical Vapor Deposition) grown GaAs epilayers on GaAs(100). Three distinct temperature-dependent regions of growth rates were identified as growth temperature was increased from 570 to 690°C. The growth rates were also strongly dependent on V/III ratio in a range of 5 to 30, which clearly indicates that the growth rate is determined by the amount of arsenic adsorbed on the surface at low V/III ratio and adsorption of TMGa or decomposition process at high V/III ratio. Hall concentration measurements and low temperature photoluminescence data show that the films are all p-type and their impurity concentrations are reduced by two orders of magnitude compared to those of epilayers grown by CBE(Chemical Beam Epitaxy) which employs TMGa and arsenic(precracked arsines) as source materials. Our results indicate that the hydrogen atoms dissociated from adsorbed arsine may remove hydrocarbon species resulting in a significant drop in hole concentration.

Carbon incorporation in GaAs and AlGaAs grown by MOMBE using trimethlgallium

In spite of the attention that growth of GaAs from trimethylgallium (TMGa) by MOMBE has received, some uncertainty exists as to the nature of the carbon incorporation process. Specifically, it is unclear what reactions control the removal of methyl radicals from the growth surface, and whether these reactions can be influenced by the addition of other species such as hydrogen. In this paper, the role of hydrogen has been investigated by introducing molecular hydrogen as well as hydrogen bonded Group III and Group V sources. None of the hydrogen sources were found to significantly reduce the carbon background, through a small amount of passivation of the carbon acceptor was observed due to incorporation of hydrogen from incompletely dissociated CH3. Significant reduction in the carbon level is observed with increasing V/III ratio. Therefore, it appears that the carbon removal process is dominated by formation of (CH3)xAs species rather than by formation of CH4. The growth kinetics of AlGaAs have also been examined and the data suggests that carbon incorporation in growth from TMGa is due to incorporation of (CH3)xGa rather than adsorbed CH3 radicals.

Ftir Studies Of Organometallic Surface Chemistry Relevant To Atomic Layer Epitaxy.

ABSTRACTThe adsorption and surface reactions of trimethylgallium and tertiarybutylarsine on GaAs(100) surfaces have been investigated by Fourier transform infrared spectroscopy. Adsorbed methyl groups resulting from the dissociative chemisorption of trimethylgallium on GaAs(100) are shown to form As-H and CH2 species on the surface. The CH2 groups are stable on the surface at temperatures as high as 550 °C. The surface coverage is low (∼0.2% of a monolayer) and is reduced by the presence of hydrogen on the surface. This dehydrogenation of surface methyl groups could be a possible route to carbon incorporation in GaAs grown by atomic layer epitaxy. Tertiarybutylarsine is shown to decompose primarily by homolysis to form a tertiary butylgroup and AsH2. At temperatures below 400°C on trimethylgallium dosed surfaces, the decomposition products appear to cause the hydrogenation of methylene groups remaining from prior surface dosing with trimethylaallium. At high temperatures, the tertiarybutyl radical appears to undergo dehydrogenation reactions to an unsaturated species which is stable on the surface. In contrast, the dehydrogenation does not appear to occur on surfaces treated with tertiarybutylarsine. The data for trimethylgallium and tertiarybutylarsine support the general assertion that surface As-H species play a critical role in the removal of hydrocarbon species from the growth surface.

Absence of 13C incorporation in 13CCl4-doped InP grown by metalorganic chemical vapor deposition

Intentional carbon doping of low-pressure metalorganic chemical vapor deposition (MOCVD) grown InP has been attempted with a 500 ppm mixture of 13CCl4 in high-purity H2, which has been used to obtain carbon-acceptor concentrations as high as 1×1019 cm−3 in GaAs. Under growth conditions similar to those used for heavy carbon incorporation in GaAs, injection of 13CCl4 into the growth reactor during growth of InP did not produce any measurable change in the carrier concentration of the InP epitaxial layers or any change in the 13C concentration above the 13C background in secondary-ion mass spectroscopy analysis. These results support previous low-temperature photoluminescence measurements of high-purity InP in which no residual carbon acceptor is observed under many growth techniques and growth conditions, and hence support the hypothesis that carbon is not incorporated in InP grown by MOCVD.

Characteristics of carbon incorporation in GaAs grown by gas source molecular beam epitaxy

Nominally undoped p-type GaAs has been grown by gas source molecular beam epitaxy (GSMBE) using triethygallium and arsine. The temperature dependence of carbon incorporation has been investigated. It has been found that there exists an optimum growth temperature (Tg) of about 550 ° C, at which the lowest carbon incorporation and the highest Hall mobility are attained. At Tg higher than 550 ° C with a V/III ratio of 5, the carrier concentration exhibits an Arrhenius type dependence on Tg with an activation energy of 2.2 eV. In contrast, when Tg is lower than 550 ° C, the carrier concentration increases with decreasing Tg. Defect induced bound exciton peaks have been observed in the photoluminescence spectra except for the sample grown at the optimum growth temperature. A qualitative model to explain the characteristics of carbon incorporation will be discussed.

Non-Hydride Group V Sources for Omvpe

AbstractA major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of II/V semiconductor materials is the hazard posed by the hydride sources, AsH3 and PH3, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the highest quality materials. The set of stringent requirements for an organometallic group V source, which includes a high vapor pressure (>50 Torr) and freedom from undesirable carbon contamination, eliminates most commonly available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire area of group V sources, including the elemental sources, for OMVPE growth of II/V materials will be reviewed. The sources with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give unacceptably high carbon incorporation, as does dimethylarsine. Diethylarsine, which has one H attached to the As, produces high quality GaAs. Tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) appear to be promising source materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures than for PH3. No carbon contamination can be attributed to the TBP. Control of the As/P ratio in OMVPE grown GaAsP is much improved for TBP as compared with PH3 due to the more rapid pyrolysis. TBAs has similar attributes including a favorable vapor pressure and lower pyrolysis temperature than AsH3. The substitution of TBAs for AsH3 results in no observable increase in carbon in the epitaxial GaAs. Phenylarsine is a similar source, with a phenyl radical substituted for a single H atom on AsH3. The vapor pressure of phenylarsine is quite low and the pyrolysis temperature is expected to be some what lower than that for AsH3. Limited results indicate that carbon incorporation in GaAs is acceptable only when TEGa is the group V source.

EL-2 Defect Formation and Carbon Incorporation in GaAs grown by Organometallic Vapor Phase Epitaxy

AbstractThe anti-site defect AsGa, EL-2, is used to understand the nature of arsenic surface species during the Organometallic Vapor Phase Epitaxy(OMVPE) of GaAs. The concentration of EL-2 in unintentionally doped n-GaAs, measured by Deep Level Transient Spectroscopy, is presented as a function of AsH3 partial pressure, TMGa partial pressure and the growth temperature. Based on this data, a model for EL-2 incorporation in OMVPE GaAs is developed in which all surface species As-H, are converted to As2 at around 765 ° C. Under the same set of growth conditions, relative carbon levels measured by 4K Photoluminescence, suggest that the increase in carbon levels with growth temperature is due to the gas-phase loss of H radical from the As-H species.

A Qualitative Model for Predicting Alkyl Stability and its Relevance to Organometallic Growth of HgCdTe and GaAlAs

ABSTRACTA qualitative stability model established for hydrocarbon molecules and extended to organometallic compounds is applied to alkyl organometallic compounds used in thin film growth. For hydrocarbon molecules the strength of a carbon-hydrogen bond is reduced by neighboring alkyl groups, The mechanism for this effect is delocalization of the unpaired electronic charge in the resultant free radical by neighboring alkyl groups. The delocalization effect is present in organometallic compounds and is illustrated here for several alkyl organometallic systems. Two applications of the delocalization effect in thin film growth are discussed. First the thermal stability of organotellurium compounds is substantially reduced in branched compounds which permits significantly lower HgCdTe metalorganic growth temperatures. Also carbon incorporation in GaAs and GaAlAs is reduced with ethyl instead of methyl organometallic compounds. An important factor contributing to this result is the weaker carbon-metal bonds in the ethyl compounds.