AVS 59th Annual International Symposium and Exhibition
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuM

Paper EM-TuM10
Characterizations of Proton-irradiated GaN and 4H-SiC by KOH Etching

Tuesday, October 30, 2012, 11:00 am, Room 009

Session: Electrical Testing and Defects in III-V’s
Presenter: H.-Y. Kim, Korea University
Authors: H.-Y. Kim, Korea University
Y.J. Shin, Korea Electrotechnology Research Institute
W. Bahng, Korea Electrotechnology Research Institute
J. Kim, Korea University
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We investigated the variations of the free electron concentrations and the etch pits such as threading screw dislocation (TSD), threading edge dislocation (TED) and mixed dislocation on proton-irradiated GaN and 4H-SiC. High energy protons create the radiation-induced defects (RD) such as single VSi, VC and interstitials, which can act as the carrier traps. Before proton irradiation, the energy loss and the penetration depth of the high-energy protons were assessed by Monte Carlo simulation (SRIM). Proton irradiations were performed on the sidewall and backside (carbon face of 4H-SiC) of the samples to examine the experimental proton-penetration depth. The irradiated fluence of the 6 and 8 MeV protons were 5x1015 cm-2. High-energy protons gradually loss their energy by Coulomb interactions until they approach to specific depth where protons collide with the lattice atoms and create the point defects. The free electron concentrations of pre-irradiated GaN and 4H-SiC were 4x1016 cm-3 and 5x1018 cm-3, respectively. The free carrier concentrations of proton irradiated GaN and SiC showed less than 1x1016 cm-3, which can be calculated from the Raman scattering. After proton irradiation, 4H-SiC was etched in molten KOH at 530 ℃ for 3 min to compare the shape of the etch pits before and after proton irradiation. It was reported that the different kinds of etch pit were apparently distinguished at low-doped SiC, while the classification of the etch pit on highly doped SiC were very difficult. We observed the effect of the free carrier concentrations to the shape and the size of the etch pits. The results of molten KOH etched proton irradiated 4H-SiC showed different etch pits which were clearly distinguished. The TSDs were approximately 2-3 times larger than TEDs in proton-irradiated sample. After 1700 ℃ thermal annealing, the free electron concentrations were partially recovered. The differences of TEDs and TSDs were less evident after thermal annealing due to the recovery of the free electron concentrations. More details will be discussed.