Electroluminescence And Photoluminescence Studies Of A Nitride-Rich GaN 1-X P x SQW Structure LED Grown By Laser-Assiste
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Electroluminescence And Photoluminescence Studies Of A Nitride-Rich GaN1-XPx SQW Structure LED Grown By Laser-Assisted Metal-Organic Chemical Vapor Deposition Junjiroh Kikawa1, Seikoh Yoshida2 and Yoshiteru Itoh2 1Fitel Phtonics Laboratory, The Furukawa Electric Co., Ltd., 8, Yawatakaigan-dori, Ichihara, Chiba, 290-5555, Japan 2Yokohama R&D Laboratories, The Furukawa Electric Co., Ltd., 2-4-3, Okano, Nishi-ku, Yokohama, 220-0073, Japan
ABSTRACT We fabricated a light-emitting diode (LED) having a nitride-rich GaN1-xPx single quantum well (SQW) structure grown using laser-assisted metal-organic chemical vapor deposition (LA-MOCVD). The peak energy of the electroluminescence (EL) of the LED was 2.88 eV, which is in the vicinity of the energy due to the recombination of the bounding exciton by P atoms, known as an isoelectronic trap in GaN. We observed a blue shift of this peak by increasing the drive current. We also observed extra emission of band-to-band recombination at about 3.4 eV above a drive current of 32 mA, where the external quantum efficiency was already saturated.
INTRODUCTION
With the success of a cation (In) mixed GaN-based blue light-emitting diode (LED) [1], there has been considerable interest in mixed-anion nitride alloys. Especially, III-V-nitrides, such as GaN1-xAsx or GaN1-xPx, and related quaternary semiconductor compounds have been particularly attractive for applications in optoelectronic devices operating over a wider range of wavelengths from ultraviolet to infrared due to a gigantic bandgap bowing compared with cation (In) mixed GaN. It has recently been reported that N-rich hexagonal GaN1-xPx could be grown on a sapphire substrate by gas-source molecular-beam epitaxy (GS-MBE) [2-4] and metal-organic chemical vapor deposition (MOCVD) [5-7]. In these compounds, the behavior of As or P atoms substituting N atoms as an isoelectronic trap, which localize the hole, has been reported. This characteristic is expected to be the recombination center of radiation or the effective path of an electron to a localized hole, competing with another non-radiative recombination center. In this paper, it is reported that we tried to grow GaN1-xPx using laser-assisted (LA)MOCVD in order to obtain an N-rich GaN1-xPx active-layer LED structure, and that we performed electroluminescence (EL) and photoluminescence (PL) measurements to clarify the role of the P atoms.
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EXPERIMENTAL
The LA-MOCVD technique was used for GaN1-xPx growth [7]. Trimethylgallium (TMG), ammonia (NH3) and tertialbuthylphosphine (TBP) were used as source gases. GaN epitaxial wafers on a sapphire (0001) C substrate were used for N-rich GaN1-xPx. The growth temperature was at around 1223 K and the sample was annealed under a temperature of around 1373 K after growth. The details of the LA-MOCVD technique are described elsewhere [6]. The structure of the GaN1-xPx LED was n-type GaN(Si)/ for GaN1-xPx /p-type GaN(Mg)/ sapphire (0001)C, and the thicknesses, which were estimated by the growth rate, were 0.1 µm for n-type GaN, 0.05 µm fo
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