Electrical and Optical Studies of Si-Implanted GaN
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Electrical and Optical Studies of Si-Implanted GaN James A. Fellows,1 Yung Kee Yeo,1 Robert L. Hengehold,1 and Leonid Krasnobaev 2 Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, U.S.A 2 Implant Sciences Corp, Wakefield, MA 01880-1246, U.S.A 1
ABSTRACT The electrical and optical properties of Si-implanted GaN have been investigated as a function of ion dose, anneal temperature, and implantation temperature using Hall-effect measurements and photoluminescence. Implantation of 200 keV Si ions was made at room temperature and 800 oC into MBE-grown GaN capped with 500 Å AlN at six different doses ranging from 1x1013 to 5x1015 cm−2. The samples were proximity cap annealed from 1050 to 1350 oC for 5 min to 20 s using either a conventional furnace or rapid thermal annealing. For a given dose, electrical activation efficiencies and mobilities increase as the anneal temperature increases from 1050 to 1350 oC. Generally, the higher the dose, the greater the activation efficiency for any given anneal temperature. For a sample implanted with a dose of 1x1015 cm−2 and annealed at 1350 oC for 20 s, an electrical activation efficiency of 100% was obtained. Exceptional carrier concentrations and mobilities were obtained on all Si-implanted samples, and a comparison of the results was made between room temperature and 800 oC implantation. Photoluminescence measurements were also performed in an effort to better understand the electrical activation behavior of the Si implants in GaN. INTRODUCTION Group-III nitrides can be used for specialized high-frequency, high-temperature, and high-power electronic devices, as well as blue to UV light emitting and detecting devices. However, the fabrication of successful devices must still overcome several important problems. One of the challenges associated with group-III nitride device technology is successfully doping impurities via ion implantation. Although ion implantation as a tool for doping semiconductors has become a mature technology in Si- and GaAs-based devices, the technique is relatively immature for GaN. While this doping technique has many advantages including independent control of the doping level, the possibility of selective area doping, and the ability to fabricate planar devices and self aligned structures, one disadvantage is the need to anneal out the implantation damage and electrically activate the implanted ions. Several activation studies of Si-implanted GaN have been reported. Edwards et. al. implanted Si at 300 oC into GaN with a total dose of 4.4x1014 cm−2, annealed at 1150 oC for 2 min, and obtained 27% electrical activation efficiency [1]. Zolper et. al. implanted GaN with Si ions at doses ranging from 5x1013 to 1x1016 cm−2, and annealed at 1100 oC for 15 s in a SiC-coated graphite susceptor. They reported negligible activation for doses below 5x1015 cm−2, but reported 50% electrical activation for a dose of 1x1016 cm−2 [2]. Dupius et. al. implanted GaN with Si ions at a dose of 5x1014 cm−2, annealed at 1150 oC for 5 min, and reported only 19%
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