Selective Epitaxial Growth Of GaAs Research Articles

Selective epitaxial growth of GaAs by current controlled liquid phase epitaxy

Selective epitaxial growth of Te-doped GaAs on circularly patterned GaAs (100) substrate was investigated by liquid phase epitaxy (LPE) and current controlled liquid phase epitaxy (CCLPE). SiNx was used as a mask layer to fabricate circular windows on the substrate and the effect of various growth periods and current densities on the growth morphology were investigated. A truncated pyramid like structure with a vertical thickness of 337μm and a lateral thickness of 268μm was achieved on the circularly patterned substrate at 6h growth with an applied current density of 20Acm−2. The vertical growth was increased almost one order and lateral growth was increased up to nine times compared to standard LPE growth. The growth step density was higher at window walls and it caused relatively higher growth compared to its centre. The surface morphology and selective epitaxial growth were greatly improved by an applied DC electric current. The dislocation density of the grown epilayer was significantly reduced when compared with that of the substrate. Solute transport in the solution was enhanced by the electromigration of solute by an electric current, which enhanced growth in vertical and lateral directions.

GaAs on Ge for CMOS

Selective epitaxial growth of GaAs on Ge is a prerequisite for the integration of GaAs and Ge in the sub-22 nm CMOS nodes. The problems encountered for epitaxial growth of GaAs on Ge are described and illustrated. Mainly the problem of anti-phase boundary (APB) formation is addressed. Selective epitaxial growth of GaAs on Ge with a SiO 2 mask is discussed and selectively grown layers are characterized by X-ray diffraction, electron microscopy, defect etching and photoluminescence spectroscopy. An optimized growth procedure is presented, which simultaneously reduces loading effects and APB creation. Low temperature photoluminescence measurements show the good quality of the selectively grown GaAs on Ge.

Selective epitaxial growth of GaAs on Ge by MOCVD

We have selectively grown thin epitaxial GaAs films on Ge substrates with the aid of a 200 nm thin SiO 2 mask layer. The selectively grown structures have lateral sizes ranging from 1 μm width up to large areas of 1×1 mm 2. The growth with the standard growth procedure for GaAs growth on Ge substrates reveals a limited amount of GaAs nucleation on the mask area and strong loading effects caused by diffusion of group III precursors over the mask area and in the gas phase. Reduction of the growth pressure inhibits GaAs nucleation on the mask area and reduces the loading effects strongly, but favors the creation of anti-phase domains (APDs) in the GaAs. An optimized growth procedure was developed, consisting of a 13 nm thin nucleation layer grown at high pressure, followed by low-pressure growth of GaAs. This optimized growth procedure inhibits the nucleation of GaAs on the mask area and is a good compromise between reduction of loading effects and inhibition of APD growth in the GaAs. X-ray diffraction and photoluminescence measurements demonstrate the good microscopic characteristics of the selectively grown layers.

Selective Epitaxial Growth of GaAs on Ge Substrates with a SiO2 Pattern

We have selectively grown thin epitaxial GaAs films on Ge substrates with the aid of a 200 nm thin SiO2 mask layer. The selectively grown structures have lateral sizes ranging from 1 μm width up to large areas of 1 by 1 mm2. The growth is fully selective, thanks to an optimized growth procedure, consisting of a 13 nm thin nucleation layer grown at high pressure, followed by low pressure growth of GaAs. This growth procedure inhibits the nucleation of GaAs on the mask area and is a good compromise between reduction of loading effects and inhibition of anti phase domain growth in the GaAs. Nevertheless, both microscopic and macroscopic loading effects can still be observed on x-section SEM images and profilometer measurements. X-ray diffraction and low temperature photoluminescence measurements demonstrate the good microscopic characteristics of the selectively grown GaAs.

Selective Epitaxial Growth of GaAs on Ge Substrates with a SiO2 Pattern

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Selective epitaxial growth of GaAs on Si with strained short-period superlattices by molecular beam epitaxy under atomic hydrogen irradiation

Selective epitaxial growth of GaAs on a Si substrate with (GaAs)m(GaP)n strained short-period superlattices (SSPSs) and GaP buffer layer was achieved by molecular beam epitaxy under atomic hydrogen irradiation. The selective epitaxial layers were grown two dimensionally so that reflection high-energy electron diffraction patterns maintained streaky patterns with no apparent transition to three-dimensional spot patterns during the selective epitaxial growth of the GaAs/SSPSs/GaP/Si structure. Therefore, generation of threading dislocations due to the three-dimensional island growth was suppressed, in spite of a large lattice mismatch. It was also confirmed that the thickness of each buffer layer was slightly increased near the edge of the masked region. Finally, the epitaxial patterns of GaAs clearly exhibit crystal facets.

Selective Growth of GaAs on GaAs (111)B Substrates by Migration-Enhanced Epitaxy

Selective epitaxial growth of GaAs on GaAs (111)B substrates masked by SiO2 has been demonstrated by using migration-enhanced epitaxy (MEE) with annealing after deposition of either Ga or As4. When annealing is performed after Ga deposition, no polycrystalline GaAs is formed on the SiO2 mask and the surface of the epitaxial layer grown in the window region is very smooth and uniform, whereas polycrystalline deposition occurs when the annealing is performed after As4 deposition. These results indicate that complete selectivity is more easily obtained by annealing after Ga deposition rather than As4 deposition. By using this method successful selective growth of GaAs has been achieved at substrate temperature around 590°C. Ga adatoms deposited on the SiO2 mask seem to evaporate or diffuse into the window region during the Ga deposition and annealing period. The conditions for successful selective growth has been established as a function of substrate temperature and Ga flux, so that smooth epitaxial layers are grown reproducibly. We also discuss the surface diffusion of Ga atoms on the SiO2 mask.

Selective epitaxial growth of GaAs using dimethylgalliumchloride by multi-wafer low-pressure metal organic vapor phase epitaxy (LP-MOVPE)

We demonstrated for the first time the selective epitaxial growth of n-GaAs using dimethylgalliumchloride (DMGaCl) by a multi-wafer LP-MOVPE system. We achieved complete selective epitaxy for the GaAs at a growth rate of more than 0.4 μm/h with an electron carrier concentration of more than 5×10 18 cm −3. The growth rate and the carrier concentration were analyzed to verify whether this process could be used for the mass-production of FET devices. The growth rate when employing DMGaCl depended less on the size of open area than in the case of a conventional trimethylgallium (TMGa) source, which is a result of the different vapor phase diffusion lengths of the used Ga-containing materials. The impurity concentrations of the selective epitaxial layers, which were measured by secondary ion mass spectrometry (SIMS), were low enough for practical FET applications.

The role of the substrate in photoenhanced metalorganic chemical vapor deposition

A GaAs laser diode has been used as the light source for the selective epitaxial growth of GaAs by photoenhanced metalorganic chemical vapor deposition (PE-MOCVD). The use of GaAs/InGaP layered structures as substrates for these experiments permitted to accurately control the availability of photoexcited carriers reaching the GaAs growth surface. The experimental results obtained rule out pure pyrolysis and photolysis as possible mechanisms responsible for the PE growth rate, and indicate that photoexcited carriers are directly involved in the PE process. The experimental data are consistent with a kinetic model that invokes surface recombination as the main physical mechanism for the PE growth rate effect.

Selective growth of GaAs/InGaP heterostrusctures by photo-enhanced organomettalic chemical vapor deposition

Selective epitaxial growth of GaAs on GaAs and In 0.49Ga 0.51P surfaces, using photo-enhanced organomettalic chemical vapor deposition, was investigated. The growth rate dependence on illumination intensity, trimethylgallium partial pressure, and temperature is reported. In-situ patterning and three-dimensional shaping during growth of GaAs/InGaP burried heterostructures, are demonstrated. The experimental results are in good agreement with a simple model, in which the decomposition of absorbed trimethylgallium is assisted by surface recombination of photo-exicited free carriers.

The role of the arsenic source in selective epitaxial growth of GaAs and AlGaAs by MOMBE

The authors have investigated the role of various arsenic precursors on the selectivity of GaAs and AlGaAs at low deposition temperatures, <or=525 degrees C, during growth by metal organic molecular beam epitaxy (MOMBE). The As2 generated from the cracking of AsH3 was found to induce nucleation on the SiN mask surface for both triethylgallium (TEG) and trimethylamine alane (TMAA). Trisdimethylaminoarsenic (DMAAs) produces identical behavior, probably due to its high decomposition efficiency, which also leaves free arsenic on the mask surface. By contrast, phenylarsine (PhAsH2) does not induce nucleation as readily due to its insufficient decomposition on the mask surface. Using PhAsh2, GaAs growth from TEG and AlGaAs growth from TMAA and trimethylgallium (TMG) were found to be highly selective. However, though selectivity was high, the surface morphology of the regrown area was typically rough due to contamination during processing. Various attempts at removing this contamination are also discussed.

Lateral Supply Mechanisms in Selective Metalorganic Chemical Vapor Deposition

Selective epitaxial growth of GaAs was carried out by atmospheric-pressure metalorganic chemical vapor deposition, and lateral supply mechanisms of reactant species from mask areas to window areas were investigated. Since reactant species arriving on SiO2 surfaces were easily reevaporated, deviation from mass balance was observed. In the case of a SiO2 mask with width of more than 20 µm, lateral vapor-phase diffusion dominated over increment of selective epilayers because of short surface-diffusion length on SiO2 surfaces (<1 µm). It was apparent experimentally and analytically that long ridged tails of selective epilayers were formed by lateral vapor-phase diffusion. Appearance of wavelike tails at mask edges was due to surface diffusion from (111)B facets. Surface-diffusion length on (111)B surfaces was estimated at 3 µm.

Surface-diffusion model in selective metalorganic chemical vapor deposition

Selective epitaxial growth of GaAs was carried out by atmospheric pressure-metalorganic chemical vapor deposition using W and SiO2 masks, and a deposition-free region was clearly observed along the edge of the masks. The surface concentration of the reactant species on the masks was analyzed by a surface-diffusion model and a new method to estimate the surface-diffusion length on the masks was proposed. The surface-diffusion length on SiO2 and W masks were 0.45 and 0.07 μm at 610 °C, respectively. The surface-diffusion length increased with decreasing the substrate temperature and became longer on the masks irradiated by an atom beam.

Selective epitaxy of MOVPE GaAs using diethyl gallium chloride

Selective epitaxy is the laterally controlled growth of epitaxial material on a substrate. We have demonstrated the highly selective epitaxial growth of GaAs using diethyl gallium chloride or (C 2H 5) 2GaCl. No GaAs growth is observed on the masking material over a wide range of growth temperatures, 600 ⩽ T ⩽800°C. The edges of the selectively grown GaAs are bounded by the slow growth planes typical of the inorganic based growth techniques. By appropriate pre-growth treatment the electrical properties of the interface between the selectively grown material and the underlying substrate can be made to be very good with no interfacial potential barrier.

A Comparison of Arsine and Tertiarybutylarsine as Precursors for the Selective Epitaxial Growth of GaAs and AlGaAs

ABSTRACTWe have investigated the use of tertiarybutylarsine (tBAs) as an As source in the surface-selective growth of GaAs and AlGaAs by low-pressure OMVPE. Deposition was carried out onto GaAs substrates partly masked with SiNx. Triethylgallium (TEGa) and trimethylaluminum (TMAl) were used as precursors along with either arsine or tBAs. Growth pressures were in the range 0.3 to 3.0 Torr. The usual trends of decreasing deposition on the mask with increasing temperature, decreasing group V/III ratio, and decreasing pressure were observed. At very low group V/III ratios, for either As precursor, single crystal material with a pitted surface was obtained. A reduction in the nucleation of polycrystalline material on the mask was observed when tBAs was used in place of AsH3.

Low-temperature selective growth of GaAs by alternately supplying molecular beam epitaxy

The selective epitaxial growth of GaAs on GaAs and no deposition on SiO 2 has been achieved at low temperatures (≥ 610°C) by supplying Ga and As 4 molecular beams alternately. The necessary growth conditions for the selective growth involving substrate temperature, growth rate and arsenic pressure have been clarified.

MBE Growth of GaAs on an Exactly (001)-Oriented Si Substrate and Selective Epitaxial Growth for Fabrication of Modulation-Doped Fet's

ABSTRACTGaAs layers free of antiphase domains (APD's) have been grown by molecular beam epitaxy (MBE) on nominally (001)-oriented Si substrates. This is achieved by preheating the substrates at 950°C over 60 min or at 1000°C over 5 min in an ultrahigh vacuum. The maximum Hall mobility at 293 K is 5300 cm2/Vs for the APD-free GaAs layer doped with Si at a concentration of 2×1016 cm−3. Selective epitaxial growth of GaAs has been carried out on a Si substrate pattrened with SiO2, which was formed by wet O2 oxidation. By choosing an appropriate thickness of the SiO2 layer, thzxcSe warpage of wafers can be reduced to zero. While single-crystalline GaAs is grown on Si-exposed areas, highly-resistive (p ≧ 105 Ωcm) poly-crystalline GaAs is deposited on SiO2. This technique has been successfully applied for the device isolation of modulation-doped FET's (MODFET's, HEMT's, etc.) on Si without mesa-etching. The transconductance of the MODFET with a 3 μm-long gate reaches 88 mS/mm at 293 K.

MBE Growth of GaAs on an Exactly (001)-Oriented Si Substrate and Selective Epitaxial Growth for Fabrication of Modulation-Doped Fet's

AbstractGaAs layers free of antiphase domains (APD's) have been grown by molecular beam epitaxy (MBE) on nominally (001)-oriented Si substrates. This is achieved by preheating the substrates at 950 °C over 60 min or at 1000 °C over 5 min in an ultrahigh vacuum. The maximum Hall mobility at 293 K is 5300 cm2 /Vs for the APD-free GaAs layer doped with Si at a concentration of 2×1016 cm−3 . Selective epitaxial growth of GaAs has been carried out on a Si substrate pattrened with SiO2, which was formed by wet O2 oxidation. By choosing an appropriate thickness of the SiO2 layer, the warpage of wafers can be reduced to zero. While single-crystalline GaAs is grown on Si-exposed areas, highly-resistive (ρ ≧ 105 Ωcm) poly-crystalline GaAs is deposited on SiO2 . This technique has been successfully applied for the device isolation of modulation-doped FET's (MODFET's, HEMT's, etc.) on Si without mesa-etching. The transconductance of the MODFET with a 3 µm-long gate reaches 88 mS/mm at 293 K.

Selective epitaxial growth of gallium arsenide by molecular beam epitaxy

GaAs was selectively grown on GaAs substrates patterned with SiO2 by conventional molecular beam epitaxy (MBE). No growth was found on SiO2, except for small GaAs particles, when the substrate temperature was above 700 °C under 1.2×10−5 Torr arsenic pressure. With the increase in the substrate temperature, the selectivity was better while the growth rate decreased. At 775 °C, no growth occurred, even on GaAs. Selective epitaxial growth of GaAs by MBE is promising for application to device fabrications.

Selective Epitaxial Growth of GaAs by Metalorganic Chemical Vapor Deposition

Films of SiO2, W and W/SiO2 have been applied as masks for the selective epitaxial growth of GaAs by metalorganic chemical vapor deposition (MOCVD). The deposition selectiveties on SiO2 masks are mainly due to a difference in the absorption coefficients of reactant species between SiO2 and GaAs, while those on W masks are due to the surface migration of reactant species. Reactant species migrating on the surfaces of W masks are (finally) used in the epitaxial growth of opening windows, and selective epitaxial growth maintaining mask surfaces completely free from deposition have been attained for samples in which mask patterns are narrower than 40 µm.