Nitride-Rich Hexagonal GaNP Growth Using Metalorganic Chemical Vapor Deposition
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NITRIDE-RICH HEXAGONAL GaNP GROWTH USING METALORGANIC CHEMICAL VAPOR DEPOSITION
Seikoh Yoshida, Yoshiteru Itoh and Junjiroh Kikawa Yokohama R&D Laboratories, The Furukawa Electric Co., Ltd. 2-4-3 Okano, Nishi-ku, Yokohama, 220-0073 Japan
ABSTRACT
The growth of GaNP using laser-assisted metalorganic chemical vapor deposition (LA-MOCVD) was carried out for the fabrication of a light-emitting diode (LED). We used an Ar-F laser in order to decompose the source gases at lower temperatures. Trimethylgallium (TMG), ammonia (NH3) and tertialybuthylphosphine (TBP) were used for the growth. GaNP growth was carried out at different temperatures. After that, annealing was carried out at 1273-1373 K to improve the crystal quality. As a result, N-rich GaNP could be grown at 1123-1223 K. The surface morphologies of GaNP were improved when the growth temperature was increased to above 1173 K. We investigated the photoluminescence (PL) of GaNP. The band-edge emission of GaNP was observed at 77 K upon applying thermal annealing at 1323 K. This peak shifted to about 0.2 eV compared with the GaN band-edge emission. Furthermore, a GaNP LED was fabricated and the electoluminescence spectra were investigated. The band-edge emission at 420 nm was observed.
INTRODUCTION
III-V-N mixed semiconductors [1-7], such as GaNP and GaNAs [8-12], are new very promising materials for light-emitting diodes (LED) over a wider range of wavelengths from ultraviolet to infrared due to a huge bandgap bowing. N-rich hexagonal GaNP grown by gas-source molecular-beam epitaxy (GSMBE) [6,7] and metalorganic chemical vapor deposition (MOCVD) [8,11,12] have recently been reported. However, there have been very few reports concerning the optical property of N-rich GaNP, except for the GaN band-edge emission of photoluminescence (PL). That is, visible-light emission based on the band-edge of GaNP has not yet been reported. Especially, GaNP crystal with a composition ratio (x) of over 1% was mainly evaluated by X-ray diffraction; the PL emission of the GaNP could not observed, since the grown crystals were poor quality. The optical properties of this alloy were only reported using P ion-implanted GaN with a P concentration of 1017-1018 cm-3 [13,14], or GaNP with a lower composition ratio (x). High-quality GaNP with a composition ratio (x) of over 1% was not obtained using MOCVD or MBE. GaNP has a very large miscibility gap resulting in difficulties for GaNP growth. We have recently reported on GaNP growth using MOCVD [15,16]. In this paper, we report on the growth of GaNP using laser-assisted (LA)-MOCVD in order to obtain N-rich GaNP with a larger composition ratio (x), as well as a GaNP LED.
G2.2.1
EXPERIMENTAL The LA-MOCVD apparatus is shown in figure 1. Trimethylgallium (TMG), ammonia (NH3) and tertialbuthylphosphine (TBP) as a phosphorus source were used as precursors. Pulsed ArF (193 nm) was also applied for the growth. The pulsed laser using an optical lens system was irradiated on the source gases on a vicinity of substrates through a quartz window. The
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