Microstructural, electrical and frequency-dependent properties of Au/p-Cu2ZnSnS4/n-GaN heterojunction

V Rajagopal Reddy; V Janardhanam; Jonghan Won; Chel-Jong Choi

doi:10.1016/j.jcis.2017.03.105

Microstructural, electrical and frequency-dependent properties of Au/p-Cu₂ZnSnS₄/n-GaN heterojunction

J Colloid Interface Sci. 2017 Aug 1:499:180-188. doi: 10.1016/j.jcis.2017.03.105. Epub 2017 Mar 29.

Authors

V Rajagopal Reddy¹, V Janardhanam², Jonghan Won³, Chel-Jong Choi⁴

Affiliations

¹ Department of Physics, Sri Venkateswara University, Tirupati 517 502, India. Electronic address: reddy_vrg@rediffmail.com.
² School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, (SPRC), Chonbuk National University, Jeonju 561-756, Republic of Korea.
³ Advanced Nano Surface Research Group, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea.
⁴ 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.

PMID: 28384536
DOI: 10.1016/j.jcis.2017.03.105

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 (N_SS) 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 N_SS. 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 N_SS estimated 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.

Keywords: Chemical properties; Electrical properties; Frequency-dependent characteristics; Heterojunction; Transport properties; p-Cu(2)ZnSnS(4); p-GaN.