Tadaaki Kaneko

Gas source molecular beam epitaxy growth of short period GaP/AlP(001) superlattices

Short period GaP/AlP superlattices are grown on GaP and GaAs substrates at 600 °C by gas source molecular beam epitaxy with growth interruption. Alternating monolayer growth of GaP and AlP is confirmed by the observation of the reflection high‐energy electron diffraction intensity oscillations during growth. The formation of short period superlattice structures and the zone‐folded LO phonons are observed in the x‐ray diffraction rocking curves and Raman spectra, respectively.

MOMBE growth characteristics of antimonide compounds

Abstract This paper describes the MOMBE (metalorganic molecular beam epitaxy) growth characteristics of antimonide compounds using TMIn (trimethylindium), TEGa (triethylgallium) and TIBAl (triisobutylaluminium) as group III sources, and As 4 , Sb 4 , TEAs (triethylarsine) and TESb (triethylstibine) as group V sources. Large differences in the growth characteristics of GaAs and GaSb MOMBE are observed. These are explained, using a theoretical consideration of the growth mechanism, by the difference in the effective surface coverage of excess As and Sb atoms during the growth. The use of TEAs and TESb instead of As 4 and Sb 4 alters the growth rate variation of both GaAs and GaSb with substrate temperature ( T sub ), which results from the interaction of alkyl Ga species with the alkyl radicals coming from the thermally cracked TEAs and TESb. The alkyl exchange reaction process is observed in the growth of AlGaSb using TIBAl and TEGa, where the incorporation rate of Al is suppressed by the coexistence of TEGa on the growth surface, in the low T sub region. This is caused by the formation of an ethyl-Al bond which is stronger than the isobutyl-Al bond. The composition and the growth rate variations of InGaSb with T sub are similar to those of InGaAs, which are closely related to the MOMBE growth process and are quite different from those of MBE (molecular beam epitaxy) and MOVPE (metalorganic vapor phase epitaxy) growth. In the MOMBE growth of InAsSb and GaAsSb using TEAs and TESb, the composition variation with T sub is weaker than that of MBE. This is a superior point of MOMBE growth for the composition control. The electrical and optical properties of MOMBE grown films as well as the quantum well structures are also described.

MOMBE (Metalorganic Molecular Beam Epitaxy) growth of InGaSb on GaSb

Abstract GaSb, InSb and InGaSb single crystalline layers have been grown on GaSb substrates, for the first time, by metalorganic molecular beam epitaxy using triethylgallium (TEGa), trimethylindium (TMIn) and solid antimony. GaSb epilayers having mirror surfaces without Ga droplets have been obtained under Sb pressures higher than the particular value, which is higher than that in the solid source MBE at the same growth rate. This is related to the TEGa pyrolysis process on the GaSb surface. The 77 K PL spectrum of GaSb grown under such conditions shows a very narrow band-to-band emission peak. InSb layers with mirror surfaces can be grown only in a narrow Sb pressure region. The In/Ga composition ratio of InGaSb is linearly dependent on the TMIn/TEGa flux ratio.

Surface diffusion lengths of Ga molecules during GaAs MOMBE (metalorganic molecular beam epitaxy) growth

Abstract Surface diffusion of Ga molecules during the MOMBE (metalorganic molecular beam epitaxy) growth of GaAs using TEGa (triethylgallium) was studied by measuring the RHEED (reflection high energy electron diffraction) intensity oscillations on the (001) GaAs vicinal surface. It is found that the obtained diffusion constant values for the MOMBE growth are the same as those for the solid source MBE growth. It is also found that the damping speed of the RHEED intensity oscillation on the (001) surface depends on the flux ratio of TEGa to Ga when both beams are supplied on the surface. It is concluded that some of the incident TEGa molecules pyrolyze into Ga atoms and migrate on the surface, that the others migrate as Ga alkyl molecules and pyrolyze at the steps or kinks, and that the diffusion lengths of Ga alkyl molecules are longer than those of Ga atoms.

Observations on RHEED intensity oscillations during the growth of GaSb and InAs by MOMBE

Abstract Reflection high-energy electron diffraction (RHEED) intensity oscillations are studied during the growth of GaSb and InAs on GaSb substrates by metalorganic molecular beam epitaxy (MOMBE) using triethylgallium (TEGa) and trimethylindium (TMIn), respectively. For the GaSb growth, the temperature dependence of the growth rate shows a monotonic increase up to 590°C, which is different from the GaAs growth. The Sb overpressure induces a drastic decrease of the growth rate at all temperatures. This behavior is explained by a lower surface site catalytic effect of GaSb surface than GaAs and by the effect of group V kinetics where excessive Sb molecules reduce the possibility for TEGa to move to proper site for bond-breaking, assuming that the rate limiting step during the GaSb growth is the first bond-breaking of TEGa. For the InAs growth, a hysteresis is observed in the phase transition for the surface reconstructions between As-stabilized (2 × 4) and In-stabilized (4 × 2). The growth rate variation with temperature shows a transport limited region above 400°C under the As-stabilized (2 × 4) conditions. Under the (4 × 2) conditions, a remarkable decrease of the growth rate is observed, which is thought to be associated with the decrease of the surface site catalytic effect.

Study of the compositional control of the antimonide alloys InGaSb and GaAsSb grown by metalorganic molecular beam epitaxy

MOMBE (metalorganic molecular beam epitaxy) growth characteristics of Sb containing ternary alloys, InGaSb, and GaAsSb are investigated. In the growth of InGaSb using TEGa (triethylgallium), TMIn (trimethylindium), and Sb4 (elemental antimony), the enhanced desorption of methyl‐In molecules at a substrate temperature Tsub of around 500 °C as well as the enhanced desorption of ethyl‐Ga molecules at around 515 °C are observed. They are due to the weak bond strength of antimonide compounds. Furthermore, the decrease of Ga solid composition with increasing Sb4 flux and the increase of GaSb partial growth rate with TMIn flow rate are also observed at as high as 500 °C. This is caused by the fact that the site blocking effect of excess Sb atoms exists up to higher Tsub. In the growth of GaAsSb using TEGa, TEAs (triethylarsine), and TESb (triethylstibine), the Sb composition versus TESb/(TEAs+TESb) curve exhibits a bowing characteristic, which is similar to that in the MOVPE (metalorganic vapor phase epitaxy) gr...

MOMBE (metalorganic molecular beam epitaxy) growth of InGaAlAsSb system on GaSb

Abstract MOMBE (metalorganic molecular beam epitaxy) growth characteristics of materials in the InGaAlAsSb system on GaSb substrates are described. The studies on GaSb growth using TEGa (triethylgallium) and solid Sb sources show that the surface reconstructions and the excess Sb on the surface play important roles in the MOMBE growth process. This is explained by a model which includes group V chemistry. The use of TESb (triethylstibine) instead of solid Sb indicates that the alkyl species coming from thermally cracked TESb also play important roles. Crystalline AlSb films are obtained using TIBAl (triisobutylaluminium), while not when using TMAl (trimethylaluminium), which is related to the difference in the reaction process. In the growth of InAsSb using TMIn (trimethylindium), TEAs (triethylarsine) and TESb, mirror-like surfaces are obtained only in the narrow TEAs/TMIn flux ratio region close to the (2×4)-(4×2) surface reconstruction transition boundary in InAs growth, and it is found that the composition of InAsSb alloy films can be controlled precisely using TMIn, TEAs and TESb. The growth characteristics of InAs and InSb are also discussed. Finally, preliminary results on the electrical and optical properties of the layers are shown to be encouraging.

Gas source MEE (migration enhanced epitaxy) growth of InP

Abstract High-quality InP layers are grown by gas source MEE (migration enhanced epitaxy) method at 350°C. It is found that even at a substrate temperature as low as 350°C, the desorption of some amount of phosphorus from the InP surface occurs when the PH 3 flow is interrupted, although the RHEED pattern is still showing the (2×4) reconstructions. As a result, the perfectly alternating supply of indium and phosphorus can be achieved only when PH 3 is supplied with a proper interruption time before the supply of In. It is also found that InP layers grown by gas source MEE at 350°C have optical properties equal to or better than those grown by conventional gas source MBE (molecular beam epitaxy) at 470°C.

MOMBE growth of GaSb and InAsSb using triethylstibine and triethylarsine

Abstract We report metalorganic molecular beam epitaxial (MOMBE) growth of GaSb and InAsSb using triethylgallium (TEGa), trimethylindium (TMIn), triethylstibine (TESb), and triethylarsine (TEAs). For GaSb growth, the maximum growth rate is observed at a substrate temperature of 500°C. This is associated with the use of TESb instead of solid Sb, where the alkyl species coming from thermally cracked TESb also play important roles in the pyrolysis of TEGa. For InAsSb growth, it is found that pyrolysis of TMIn at substrate temperatures below 400°C is decomposition limited. Precise control of solid composition for InAs 1−x Sb x in the range of 0≤ χ ≤0.6 is confirmed in the temperature range from 400 to 500°C.

Improved Growth Kinetic Model for Metalorganic Molecular Beam Epitaxy Using Triethylgallium

An improved growth kinetic model for the MOMBE (metalorganic molecular beam epitaxy) of GaAs and GaSb using TEGa (triethylgallium) is proposed. This model can reproduce simultaneously the experimental curves of the growth rate variation with substrate temperature and group V flux and the desorption rate variation of TEGa and DEGa with substrate temperature, particularly the low-temperature decomposition of TEGa to DEGa. It is found that the decomposition reaction of MEGa to Ga is a rate-limiting process, and that the difference in the growth characteristics between GaAs and GaSb is caused by the difference in the suppression effect of excess group V atoms on the decomposition process of DEGa due to the difference in the desorption parameters of As and Sb. It is also found that the decrease of the growth rate at high temperatures is caused by a rapid increase of the rate constant for the desorption of DEGa and that the nonlinear variation of growth rate with TEGa flux in the intermediate temperature region is caused by the second-order recombination process of MEGa with Et radicals.