Effect Of Implantation Temperature On Damage Accumulation In Ar - Implanted GaN
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Internet Journal Nitride Semiconductor Research
Effect Of Implantation Temperature On Damage Accumulation In Ar - Implanted GaN I. Usov1, N. Parikh1, D.B. Thomson2 and Robert F. Davis2 1Curriculum 2Department
in Applied and Materials Sciences, University of North Carolina at Chapel Hill, of Materials Science and Engineering, North Carolina State University,
(Received Wednesday, October 9, 2002; accepted Tuesday, December 17, 2002)
A systematic investigation of damage accumulation in GaN films induced by Ar+ as a function of implantation temperature and dose rate has been conducted. Depth distribution of disorder was measured by Rutherford Backscattering/Channeling spectrometry. Two disordered regions were identified in the damage depth distribution: a surface peak and a bulk damage peak. These regions exhibited different behavior as a function of implantation temperature. The displaced atomic density in the bulk damage peak displayed a “reverse annealing” behavior in temperature range from 500 °C to 700 °C, which we attributed to formation of characteristic secondary defects. The influence of implantation temperature and dose rate on the radiation damage accumulation is discussed.
1
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, controllable doping and formation of semi insulating layers must be achieved. Ion implantation is the only technique presently available for planar selective area doping of GaN [1]. The introduction of dopants into solids by ion implantation is accompanied by radiation damage of the crystalline lattice, which has to be recovered via annealing treatments. It has been demonstrated that the removal of implantation damage in GaN requires annealing temperatures above 1500 °C and is complicated by material decomposition due to nitrogen evaporation [2]. One way to facilitate the annealing process is to reduce the damage concentration by performing the ion implantation at elevated temperatures. It has been shown in a number of papers that ion implantation at temperatures (Timp) up to 550 °C reduces the amount of radiation damage in comparison to room temperature (RT) [3] [4] [5]. In contrast, a report by Wenzel et al. [6] indicated that the lattice disorder measured by Rutherford Backscattering/Channeling spectrometry (RBS/ C) in GaN implanted with Mg+ increased with increasing implantation temperature from RT to 550 °C. The main intention of the present study, therefore, was to investigate in detail the dependence on the implantation
temperature of the amount of damage produced in GaN over a wide temperature range. 2
Experimental Details
For the present investigation, epitaxial GaN films (1.0 1.5 µm thick) were grown on (0001) 6H-SiC substrates by MOVPE deposition. Implantation with 150 keV Ar+ was performed at temperatures ranging from RT to 1000 °C, to a dose of 3x1015 cm-2 and a dose rate 0.45 and 4.5 µA/cm2. During implantation the tilt angle between the ion beam di
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