Yoshito Kawakyu

UV Absorption Spectra of Adlayers of Trimethylgallium and Arsine

The UV absorption spectra of trimethylgallium (TMG) and arsine adsorbed on silica were investigated. The spectrum of the physisorbed layers of TMG and arsine were similar to the corresponding vapor spectra. On the other hand, the spectrum of the chemisorbed TMG layer was quite different. from that of vapor. Arsine can be chemisorbed on the chemisorbed TMG layer, although it cannot be chemisorbed on silica. The spectrum of the co-chemisorbed layer, consisting of TMG and arsine, was found to extend greatly to longer wavelengths.

GaAs Atomic Layer Epitaxy Using the KrF Excimer Laser

Complete self-limiting monolayer growth was achieved successfully in GaAs atomic layer epitaxy (ALE) using a KrF excimer laser. In thermal growth without laser irradiation, monolayer growth was achieved only for an extremely narrow temperature range around 500°C. With laser irradiation, monolayer growth was achieved for a relatively wide temperature range from 470°C to 530°C. The expanded temperature range for ALE under laser irradiation suggests an enhanced decomposition of Ga-containing adsorbates due to the photochemical effect, but not the thermal effect.

Surface reaction mechanisms in GaAs atomic layer epitaxy

Abstract The reactions of trimethyl gallium (TMG) on a gallium-rich surface (Ga surface) and an arsenic-rich surface (As surface) of (001)GaAs were studied using quadrupole mass spectrometry (QMS) by temperature programmed desorption (TPD) and the response of desorbed species from the surfaces during the exposure of TMG under a constant temperature. It has been found that TMG is adsorbed and decomposed on both the As and the Ga surfaces in the temperature region where atomic layer epitaxy (ALE) growth can occur. It has also been found that even the decomposed species, i.e. Me n Ga( n =1, 2), can be desorbed from the Ga surface together with TMG molecules, but not from the As surface. The results are inconsistent with the prevalent model based on selective adsorption on the As surface, and so a new selective desorption model is instead proposed for the self-limiting deposition of Ga for ALE growth. This model emphasizes that even Ga-containing decomposition products, i.e. Me n Ga( n =1, 2), are desorbed selectively from the Ga surface.

UV absorption spectra of adlayers of MOCVD source gases

Abstract The UV absorption spectra of trimethylgallium (TMG), trimethylaluminum (TMA), and arsine were investigated, regarding the temperature dependences of the vapor spectra and the spectral change by adsorption. The physisorbed layer spectrum of TMA is quite different from the vapor spectrum, but that of TMG or arsine is similar to the vapor spectrum. It was found that TMA was physisorbed on silica as a monomer. On the other hand, the chemisorbed layer spectra for TMA and TMG were different from the vapor spectra. Arsine can be chemisorbed on the chemisorbed TMG layer, but not on silica. The spectrum of the co-chemisorbed layer, consisting of TMG and arsine, has been found to extend greatly to longer wavelengths. This suggests that light irradiation can selectively decompose TMG on As in the substrate surface in a GaAs MOCVD chamber, which is an elementary process for atomic layer epitaxy.

Selective Deposition of Silicon by Mercury Sensitized Photochemical Vapor Deposition

The authors have developed a low-temperature process for selective deposition of silicon by mercury sensitized photochemical vapor deposition (Photo-CVD) without using ultraclean technology. It was found that hydrogen radical pretreatment was required to obtain selective deposition. There was an incubation period for not only SiO2 surface but also Si surface. It was confirmed that mercury sensitized Photo-CVD is a promising method for selective deposition process at low temperature using large-area glass substrate.

Low pressure metalorganic chemical vapor deposition of InGaP using tertiarybutylphosphine

Abstract Alloy composition controllability and V/III ratio influence upon crystal quality have been studied for low pressure metalorganic chemical vapor deposition (MOCVD) of InGaP using tertiarybutylphosphine (TBP). The relationship between lattice mismatch and vapor phase composition for the growth using TBP was almost the same as for the growth using PH3 InGaP epilayers, with completely mirror-like surfaces, were obtained, suggesting that undersirable prereactions between TBP and group III precursors were suppressed in low pressure MOCVD using TBP. High quality undoped and Zn-doped InGaP epilayers were obtained at a low V/III ratio of 20. It was confirmed that TBP had the possibility of being an alternative precursor to PH3 for low pressure MOCVD of InGaP lattice-matched with GaAs.

KrF Excimer Laser Irradiation Effect on GaAs Atomic Layer Epitaxy

The KrF excimer laser irradiation effect on GaAs ALE was investigated by the surface process model. It was confirmed that the decomposition rate of TMG adsorbed on the surface As atoms was increased, and its activation energy was decreased due to KrF excimer laser irradiation. In selective growth using substrates partially masked with SiO2, it was found that a large amount of TMG molecules diffused to the GaAs surface from the SiO2 mask in a low temperature range, but very few TMG molecules diffused to the GaAs surface from the SiO2 mask in a high temperature range.

Trimethylgallium Reactions on As-Stabilized and Ga-Stabilized GaAs(100) Surfaces

We compared the trimethylgallium (TMG) reaction on an As-stabilized surface of GaAs with that on a Ga-stabilized surface using a quadrupole mass spectrometer equipped with a cold aperture. It was found that, although TMG thermally decomposed on both the As-stabilized and Ga-stabilized surfaces, Ga-containing decomposition products did not desorb from the As-rich surface. A new growth mechanism for GaAs atomic layer epitaxy, related to this desorption difference, is also discussed.

Effect of oxygen on photoluminescence properties of a-Si:C:O:H film

Abstract Photoluminescence properties of a-Si:C:O:H films were investigated. a-Si:C:O:H films were prepared by glow discharge decomposition of TMS and O2 gas mixture. The PL peak position shifts to higher photon energy and relative PL intensity increases. Also, the optical band gap shifts towards higher photon energy. These tendencies are caused by oxygen atom incorporation into the films.

Metalorganic Chemical Vapor Deposition of InAlP Using Tertiarybutylphosphine

The InAlP growth by metalorganic chemical vapor deposition using tertiarybutylphosphine is reported for the first time. Films with mirrorlike surface morphology were obtained at 650°C. In comparision with phosphine, tertiarybutylphosphine is more suitable for growth at lower temperature.