Revealing the TMA2SnI4/GaN band alignment and carrier transfer across the interface

Abstract

In this study, we investigate the electronic properties of the GaN junction with TMA₂SnI₄ – (2-thiophene)methylammonium tin iodide, a Pb-free 2D perovskite. Through spectroscopic analysis, we explore the impact of TMA₂SnI₄ on surface Fermi level pinning on Ga-polar GaN surfaces, revealing insights into carrier transfer at the interface. Our findings demonstrate that TMA₂SnI₄ induces an upward shift in the surface Fermi level of GaN, resulting in a reduction in the surface barrier for electrons and an increase for holes. This indicates electron transfer from TMA₂SnI₄ to GaN and hole transfer in the opposite direction. Furthermore, utilizing ultraviolet photoelectron spectroscopy, we determine the positions of the conduction and valence bands in TMA₂SnI₄ relative to the vacuum level to be −3.05 eV and −5.2 eV, respectively. Based on these findings, we identify a type II band alignment at the TMA₂SnI₄/GaN interface, with band offsets of 0.2 eV and 1.5 eV for the conduction and valence bands, respectively. These electronic properties make the TMA₂SnI₄/GaN junction a promising candidate for active regions in optoelectronic devices, such as photodetectors and photonic synapses.