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

An Au/Cu 2 ZnSnS 4 (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 1.55 eV. 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 (0.82 eV) compared to the Au/n-GaN SJ (0.69 eV), 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 1 kHz–1 MHz, 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. [ABSTRACT FROM AUTHOR]