Clarifying the atomic origin of electron killers in β-Ga₂O₃ from the first-principles study of electron capture rates

Abstract

The emerging wide bandgap semiconductor -Ga2O3 has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors. Deep-level defects in -Ga2O3 have been intensively studied towards improving device performance. Deep-level signatures E 1, E 2, and E 3 with energy positions of 0.55–0.63, 0.74–0.81, and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated, but their atomic origins are still under debate. In this work, we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates, Ti and Fe substituting Ga on a tetrahedral site (TiGaI and FeGaI) and an octahedral site (TiGaII and FeGaII), to experimentally measured results. The first-principles approach predicted electron capture cross-sections of TiGaI and TiGaII defects are 8.56 × 10–14 and 2.97 × 10–13 cm2, in good agreement with the experimental values of E 1 and E 3 centers, respectively. We, therefore, confirmed that E 1 and E 3 centers are indeed associated with TiGaI and TiGaII defects, respectively. Whereas the predicted electron capture cross-sections of FeGa defect are two orders of magnitude larger than the experimental value of the E 2, indicating E 2 may have other origins like CGa and Gai, rather than common believed FeGa.

Perspective on electrically active defects in β-Ga2O3 from deep-level transient spectroscopy and first-principles calculations

“…Based on comparison with predicted capture cross sections, a Ti Ga1 origin has also been suggested. 76 The donor level of Ti Ga1 (E i ¼ 0:62 eV with E b ¼ 0:11 eV) is indeed close to the E 1 level and consistent with the observed Poole-Frenkel emission. 51 However, this model does not explain the observed response to heat treatments in H 2 .…”

A review of first-principles calculation methods for defects in semiconductors

“…第一性原理计算有助于 从原子尺度理解和预测材料电学、光学、磁学等诸 多性质, 近年来在半导体材料设计中正在发挥着越 来越大的作用 [20,21] , 尤其对半导体光电子和微电子 材料发展作出了重要贡献 [22] . 在半导体缺陷计算 方面, 第一性原理计算同样发挥着不可取代的作用 [23] , 使我们在几乎不需要先验假设的情况下, 对缺陷的 原子和电子结构产生清晰的认识, 既弥补了实验上 缺陷分辨能力不足的短板, 辅助解释实验现象, 确 定缺陷类型, 同时可以提供目前实验手段无法获得 的数据, 完善人们对缺陷结构和性质的理解 [24][25][26] . 尽管第一性原理计算已经成为研究缺陷和杂 质的有效方法, 目前该领域仍然存在诸多困难, 如 带电缺陷的镜像电荷作用, 密度泛函近似造成的带 隙误差等 [23] .…”