Heteroepitaxial Growth of a Wide Gap P-type Oxysulfide, LaCuOS
- PDF / 358,585 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 184 Views
V6.9.1
Heteroepitaxial Growth of a Wide Gap P-type Oxysulfide, LaCuOS Hidenori Hiramatsu 1, 2, Kazushige Ueda 1, Hiromichi Ohta 2, Masahiro Hirano 2, and Hideo Hosono 1, 2 1
Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan. 2 Hosono Transparent ElectroActive Materials (TEAM) Project, ERATO, JST, 3-2-1 Sakado, Takatsu, Kawasaki 213-0012, Japan. ABSTRACT Epitaxial films of LaCuOS, a wide gap p-type semiconductor, were grown on yittria- stabilized-zirconia (YSZ) (001) or MgO (001) substrates by a reactive solid phase epitaxy (R-SPE) method. Crystal quality, electrical and optical properties on the epitaxial films on each substrate are examined in this paper. Achievement of the heteroepitaxial growth of LaCuOS on the MgO (001) substrate improves optical properties of LaCuOS such as spectral bandwidths and emission intensity, suggesting that the MgO (001) substrate is more preferable than the YSZ (001) for epitaxial growth substrate for LaCuOS. INTRODUCTION P-type wide gap semiconductors are inevitable for the fabrication of optoelectronic devices operating at short wavelength. A layered compound of LaCuOS oxysulfide [1] is a p-type semiconductor with a wide direct transition energy gap of ~ 3.1 eV [2]. Because this material emits ultraviolet (UV) light associated with room-temperature exciton, which is stable due to its large exciton binding energy [3, 4], it offers promise as an active layer of near-UV light emitting devices. We previously prepared randomly oriented polycrystalline films of LaCuOS on SiO2 glass substrates by using an rf sputtering technique following by a postannealing [5, 6]. However, the electrical and optical properties of the films proved inadequate for optoelectronic devices, probably due to the poor crystallinity nature of the films. Therefore, epitaxial film growth was critically important for the fabrication of LaCuOS-based optoelectronic devices. Recently, we developed a unique heteroepitaxial growth method, named as a “reactive solid phase epitaxy (R-SPE)” [7, 8] and succeeded in heteroepitaxial growth of LaCuOS on yittria-stabilized-zirconia (YSZ) or MgO (001) substrates by extending its technical concept to this material [9]. In this paper, crystal quality, electrical and optical properties of the LaCuOS epitaxial films are examined in detail. EXPERIMENTAL Epitaxial LaCuOS films were prepared by the R-SPE method. First, thin metallic copper, grown as the epitaxy template [7, 8], was deposited on YSZ or MgO (001) substrates by a pulsed laser deposition (PLD) technique. Then the amorphous LaCuOS layer (~150nm) was deposited on the thin copper layer. This resulting bi-layer film was annealed at 1000 oC in an evacuated SiO2 glass tube. Details of the preparation
V6.9.2
conditions have been described in a previous paper [9]. Crystallographic orientation of the epitaxial films was analyzed by a high-resolution X-ray diffraction (HR-XRD) apparatus (ATX-G, RIGAKU Co.). HR-XRD patterns of ω-2θ radial scans and the rocking curve
Data Loading...
