Characterization of deep levels in a-plane GaN epi-layers grown using various growth techniques |
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Authors: | Hooyoung Song Eun Kyu Kim Kwang Hyeon Baik Sung-Min Hwang Yong Woon Jang Jeong Yong Lee |
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Institution: | 1. Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea;2. Optoelectronics laboratory, Korea Electronics Technology Institute, Gyeonggi-do 463816, Republic of Korea;3. Department of Materials Science and Engineering, KAIST, Daejeon 305701, Republic of Korea |
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Abstract: | To study the correlation between defects and deep levels in a-plane GaN films grown on r-plane sapphire substrates, transmission electron microscopy (TEM) and deep level transient spectroscopy (DLTS) have been performed on three types of a-plane GaN samples grown using modified two-step growth (sample I), SiNx interlayer (sample II), and patterned insulator on sapphire substrate (sample III). From the microstructure evolution in cross-sectional TEM images, it was shown that combination of growth techniques is highly efficient in the reduction of dislocation densities. Average dislocation densities of samples I, II, and III were about 2.2×109 cm?2, 1.1×109 cm?2, and 3.4×108 cm?2, respectively. The trap at Ec–Et~0.13 eV (E1) was observed in only sample I, and three electron traps at 0.28–0.33 eV (E2), 0.52–0.58 eV (E3), and 0.89–0.95 eV (E4) from the conduction band edge were measured common to all the samples. The analysis of trap properties indicated that E2 and E3 trap levels are strongly associated with the partial dislocations in a-plane GaN films. |
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