Defect emission and its dipole orientation in layered ternary Znln2S4 semiconductor

TL;DR

This study investigates defect-induced emission and dipole orientation in layered Znln2S4 semiconductors, revealing tunable defect emission properties and in-plane dipole orientation, which are promising for optoelectronic applications.

Contribution

It provides a comprehensive analysis of defect effects on electronic and optical properties of 2D Znln2S4, including defect emission tunability and dipole orientation, which were previously unclear.

Findings

Zn-In anti-structural defects create donor and acceptor levels inside the bandgap.

Defect emission can be significantly tuned by electrostatic gating.

Layer-dependent in-plane dipole orientation of defect emission was directly observed.

Abstract

Defect engineering is promising to tailor the physical properties of two-dimensional (2D) semiconductors for function-oriented electronics and optoelectronics. Compared with the extensively studied 2D binary materials, the origin of defects and their influence on physical properties of 2D ternary semiconductors have not been clarified. In this work, we thoroughly studied the effect of defects on the electronic structure and optical properties of few-layer hexagonal Znln2S4 via versatile spectroscopic tools in combination with theoretical calculations. It has been demonstrated that the Zn-In anti-structural defects induce the formation of a series of donor and acceptor levels inside the bandgap, leading to rich recombination paths for defect emission and extrinsic absorption. Impressively, the emission of donor-acceptor pair (DAP) in Znln2S4 can be significantly tailored by electrostatic gating due to efficient tunability of Fermi level (Ef). Furthermore, the layer-dependent dipole orientation of defect emission in Znln2S4 was directly revealed by back focal plane (BFP) imagining, where it presents obviously in-plane dipole orientation within a dozen layers thickness of Znln2S4. These unique features of defects in Znln2S4 including extrinsic absorption, rich recombination paths, gate tunability and in-plane dipole orientation will definitely benefit to the advanced orientation-functional optoelectronic applications.