Properties of Gallium Disorder and Gold Implants in GaN
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Properties of Gallium Disorder and Gold Implants in GaN W. Jiang, W.J. Weber, S. Thevuthasan, and V. Shutthanandan Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, U.S.A. ABSTRACT Epitaxial single-crystal GaN films on sapphire were implanted 60° off the surface normal with 1 MeV Au2+ or 3 MeV Au3+ over a fluence range from 0.88 to 86.2 ions/nm2 at 180 and 300 K. The implantation damage was studied in-situ using 2 MeV He+ Rutherford backscattering spectrometry in channeling geometry (RBS/C). The disordering rate in the nearsurface region is faster than at the damage peak. In all cases, results show an intermediate stage of Ga disorder saturation at the damage peak. During the thermal annealing at 870 K for 20 min, some Au implants in GaN diffuse into the amorphized surface region, while the remaining Au atoms distribute around the mean ion-projected-range. These results suggest a high mobility of both Ga defects and Au implants in GaN. Deeper damage implantation by 3 MeV Au3+ indicates that GaN cannot be completely amorphized up to the highest ion fluence (86.2 ions/nm2) applied at 300 K. INTRODUCTION Considerable effort has been devoted recently to the study of gallium nitride (GaN) and related materials worldwide because of their great potential for applications in advanced electronics and optoelectronics. These applications [1] include full-color displays, high-density information storage, solar-blind ultraviolet detectors, microwave power and ultrahigh power switches. Ion implantation is an important process in device fabrication. This method offers the advantages of both doping with desired elements in selective areas and precise control of dopant concentration over a well-defined depth distribution. However, ion implantation inevitably produces lattice disorder, which adversely affects the performance of any device. Fundamental research on implantation damage and dopant behavior in GaN has significant implications for the fast growing GaN industry. Previous studies have employed various irradiation sources, such as lasers [2], electrons [3], protons [4] and heavier ion species (e.g. C [5], O [6], Mg and Si [7], Ar and Ca [8], Er [9] and Au [5,10]). Most of these studies were primarily concerned about electrical or optical properties, or the damage buildup in irradiated GaN. This paper reports the effects of Au implantation on structure and thermal defect properties, as well as the temperature response of Au depth profiles in the irradiated GaN. EXPERIMENTAL PROCEDURES The n-type GaN single-crystal films (~2.0 µm thick) used in the present investigation were epitaxially grown by Metal Organic Vapor Phase Epitaxy on sapphire substrates and possessed a high crystalline quality with a minimum yield of ~1.7% for Ga sublattice. Both ion implantation and in-situ RBS/C measurements on these -oriented films were performed within the O5.9.1
Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory. Specimens were irradiated 60° off surface normal at either 180 or 3
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