title: Microstructural, electrical and frequency-dependent properties of Au/p-Cu2ZnSnS4/n-GaN heterojunction.
abstract: An Au/Cu2ZnSnS4(CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, I-V and C-V measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82eV) compared to the Au/n-GaN SJ (0.69eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by I-V, Cheung's and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density (NSS) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of NSS. Moreover, the capacitance-frequency (C-f) and conductance-frequency (G-f) characteristics of SJ and HJ are measured in the range of 1kHz-1MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the NSSestimated from C-f and G-f characteristics is lower compared to those estimated from I-V characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer.
authors.affiliation: Department of Physics, Sri Venkateswara University, Tirupati 517 502, India. Electronic address: reddy_vrg@rediffmail.com.
authors.forename: V
authors.initials: V
authors.lastname: Rajagopal Reddy
authors.affiliation: School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, (SPRC), Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: V
authors.initials: V
authors.lastname: Janardhanam
authors.affiliation: Advanced Nano Surface Research Group, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea.
authors.forename: Jonghan
authors.initials: J
authors.lastname: Won
authors.affiliation: School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, (SPRC), Chonbuk National University, Jeonju 561-756, Republic of Korea. Electronic address: cjchoi@chonbuk.ac.kr.
authors.forename: Chel-Jong
authors.initials: CJ
authors.lastname: Choi
keywords: Chemical properties; Electrical properties; Frequency-dependent characteristics; Heterojunction; Transport properties; p-Cu(2)ZnSnS(4); p-GaN