| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeP |
| Session: | Thin Films Posters Session II |
| Presenter: | Katsuhiro Uesugi, Muroran Institute of Technology, Japan |
| Authors: | K. Uesugi, Muroran Institute of Technology, Japan T. Ozawa, Muroran Institute of Technology, Japan Y. Igarashi, Muroran Institute of Technology, Japan Y. Shimomura, Muroran Institute of Technology, Japan S. Kimura, Muroran Institute of Technology, Japan K. Obara, Muroran Institute of Technology, Japan |
| Correspondent: | Click to Email |
The development of strain relaxation buffer layers between GaAs and Si(110) that controlled large lattice mismatch and surface orientation influences are expected to integrate GaAs-based optical-fiber communication devices to Si(110) wafers. The growth of Ge and GeSi layers is mainly studied on Si(001) substrates, but absorb light signal of 1.55 μm wavelength due to the narrow bandgap energy of ~0.67 eV. A two-dimensional growth technique of GaAs(110) films on Si(110) surfaces is also necessary. In this paper, we report the migration-enhanced epitaxy of n-type GaAsNSe thin films with Ga droplets prepared on Si substrate surfaces, as the strain relaxation layers between GaAs and Si(110).
GaAsNSe films were grown by using metal-organic molecular beam epitaxy (MOMBE) equipped with the nitrogen radio-frequency discharge plasma system. MO precursors used were triethylgallium, trisdimethylaminoarsenic (TDMAAs), trisdimethylaminoantimony (TDMASb), and ditertiarybutylselenide. The Si(110) substrate surfaces were thermally cleaned at 550 °C with the simultaneous supply of TDMAAs. Ga droplets were formed on Sb-terminated Si surfaces which prepared by the supply of TDMASb at the substrate temperature of 470 °C. Then GaAsNSe films were grown at the temperature of 370-510 °C. The growth process of the films was characterized by using RHEED, AFM, and x-ray diffraction methods.
The Si- and As-terminated Si(110) surfaces were not covered with Ga layers, and Ga droplets of 40-75 nm height were formed at a density of 1×108 cm-2. On the other hand, small Ga droplets of 2 nm height were formed on the Sb-terminated Si surfaces at a high density of 2×1010 cm-2, which suggest the anti-surfactant effect of Sb surface atom. The growth of a GaAsNSe ring structure occurred by the isotropic Ga diffusion from the droplet at low temperature. The step-flow growth mode of GaAsNSe was promoted as the increase of growth temperature. The activation energy of the Ga diffusion from the droplet during the growth was estimated to be 0.46 eV. At a high growth temperature of 510 °C, the two-dimensional growth of GaAsSe(110) with a large lattice mismatch of 3.5% was promoted considerably by using the effect of the surface Ga diffusion from the droplets. The formation of the pits and three-dimensional islands was suppressed in comparison with the films prepared by normal MOMBE growth. The migration enhanced MOMBE using surface Ga nano-droplets is a very useful technique for the fabrication of the flat GaAsNSe lattice relaxation layers on Si(110) substrates.