Reverse-annealing phenomenon during the high-temperature implantation of Ar + into GaN
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Reverse-annealing phenomenon during the high-temperature implantation of Ar+ into GaN Igor O. Usov1, Nalin R. Parikh1, Darren Thomson2, Robert F. Davis2 1 Curriculum in Applied and Materials Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-3287, U.S.A. 2 Deptartment of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27695-7919, U.S.A.
ABSTRACT
A systematic investigation of the damage accumulation in GaN films induced by 150keV Ar ions as a function of implantation temperature and dose rate has been conducted. The depth distribution of the disorder in the Ga sublattice has been measured by RBS/channeling spectrometry with a glancing angle detector geometry to provide enhanced depth resolution. Two disordered regions were identified in the damage depth distribution: a near-surface peak and a bulk damage peak. These regions exhibit different behavior as a function of implantation temperature. The height of the near-surface peak, as expected, decreased with implantation temperature approaching the magnitude of the unimplanted sample. The displaced atomic density in the bulk damage peak also followed this tendency and decreased in the temperature range from room temperature to 500oC. The implantation at higher temperatures resulted in an increase in the amount of damage, reaching a maximum at about 700oC and displayed a characteristic “reverse annealing” behavior. Further increase of the implantation temperature to 1000oC reduced the disorder. The influence of the dose rate and implantation temperature on the radiation damage accumulation is discussed.
INTRODUCTION
Due to its outstanding properties GaN plays a significant role in modern semiconductor physics and technology. In order to realize the advantage of GaN a controllable n- and p-type doping as well a formation of semi insulating layers must be achieved. For planar selective area doping ion implantation is the only technique presently available for GaN [1]. The introduction of dopants into solids by ion implantation is accompanied by the radiation damage of the crystalline lattice, which has to be recovered via annealing treatments. It has been demonstrated, that the removal of implantation damages in GaN requires annealing temperatures above 1500oC and is complicated by the material decomposition due to nitrogen evaporation [2]. One way to facilitate the annealing process is to reduce the concentration of residual damages (after implantation) by performing the ion implantation at elevated temperatures. It has been shown in a number of papers, that ion bombardment at the temperatures up to 55 0oC reduces the amount of radiation damages in comparison to room temperature (RT) [3-5]. In contrast, a report by Wenzel et.al. [6] indicated that the lattice disorder measured by RBS/C in GaN implanted with Mg ions increases with increasing implantation temperature from RT to 550oC. The main I11.12.1
intention of the present study, therefore, was to investigate in detail the dependence of amount of residua
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