The Properties of a P-Implanted GaN Light-Emitting Diode
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The Properties of a P-Implanted GaN Light-Emitting Diode J. Kikawa, S. Yoshida, and Y. Itoh Yokohama R&D Laboratories, The Furukawa Electric Co., Ltd. 2-4-3, Okano, Nishi-ku, Yokohama, 220-0073, Japan ABSTRACT Electroluminescence measurements of P-implanted GaN light-emitting diodes were performed. The measured peak densities of P in the GaN were 5x1020 cm-3 and 4x1021 cm-3 based on secondary ion mass spectroscopy. The EL spectra had a broad blue-band emission at the peak energy from around 2.8 eV to 3.3 eV and yellow-band emission at an energy centered at 2.2 eV. The blue-band emission could decompose into two components at energy positions of 2.9 eV and 3.2 eV. The former component is considered to be emission due to the recombination of the bounding exciton by P atoms, known as an isoelectronic trap in GaN. INTRODUCTION Gallium nitride (GaN) and its cation mixed alloys offer a host of important applications in optoelectronic devices. Recently, there has been considerable interest in mixed-anion nitride alloys, such as GaN1-xAsx or GaN1-xPx, and related quaternary semiconductor compounds, because they have a gigantic band-gap bowing compared with mixed-cation GaN. There is a possibility for applications in optoelectronic devices operating at wavelengths from ultraviolet to infrared. It has been reported that N-rich hexagonal GaN1-xPx could be grown on a sapphire substrate by gas-source molecular-beam epitaxy (GS-MBE) [1] and metal-organic chemical vapor deposition (MOCVD) [2]. There have also been several experimental reports concerning luminescence originating from As atoms in GaN. Li et al [3] observed emission at an energy position of 2.583 eV from As-doped GaN grown by metal organic vapor phase epitaxy (MOVPE); Winser et al [4] also observed strong blue emission at an energy of around 2.6 eV from As-doped GaN by MBE. On the other hand, Pankove et al [5] and Jadwisienczk et al [6] reported on the luminescence of P atoms implanted in GaN. Thus as though there have been many studies on the luminescence of these compounds, on the electro-luminescence (EL) studies have been few. In this paper, it is reported that we tried to make a GaN1-xPx active layer light emitting diode (LED) using a P-atom implanting technique, and performed EL measurements. EXPERIMENTAL In these studies we used a single crystal of GaN epitaxial wafers grown by an ordinary metal organic chemical vapour deposition (MOCVD) technique on the basal plane of sapphire substrates. The GaN wafers were high quality p-type with the yellowing structure: GaN: Mg 2.5 µm / undoped GaN 0.5 µm / undoped AlN 0.04 µm / sapphire. The concentration of Mg was 1x1019 cm-3. The wafers were implanted at room temperature with P+ ions with a dose of 2x1015 ions/cm2 at 35 keV for sample #390
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and with a dose 4x1014 ions/cm2 at 30 keV for sample #387. The implanting ion beam was inclined at 7 degrees to the normal to the GaN epitaxial layers to prevent channeling. Wafers were then grown on a Si-doped GaN epitaxial layer by ordinary MOCVD with 0.15µm t
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