Imajo Toshifumi, Ishiyama Takamitsu, Nozawa Koki, Suemasu Takashi, Toko Kaoru
Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
JSPS Research Fellow, 8 Ichiban-cho, Chiyoda-ku, Tokyo, 102-8472, Japan.
Sci Rep. 2022 Sep 2;12(1):14941. doi: 10.1038/s41598-022-19221-5.
Polycrystalline Ge thin films have recently attracted renewed attention as a material for various electronic and optical devices. However, the difficulty in the Fermi level control of polycrystalline Ge films owing to their high density of defect-induced acceptors has limited their application in the aforementioned devices. Here, we experimentally estimated the origin of acceptor defects by significantly modulating the crystallinity and electrical properties of polycrystalline Ge layers and investigating their correlation. Our proposed linear regression analysis method, which is based on deriving the acceptor levels and their densities from the temperature dependence of the hole concentration, revealed the presence of two different acceptor levels. A systematic analysis of the effects of grain size and post annealing on the hole concentration suggests that deep acceptor levels (53-103 meV) could be attributed to dangling bonds located at grain boundaries, whereas shallow acceptor levels (< 15 meV) could be attributed to vacancies in grains. Thus, this study proposed a machine learning-based simulation method that can be widely applied in the analysis of physical properties, and can provide insights into the understanding and control of acceptor defects in polycrystalline Ge thin films.
多晶锗薄膜作为一种用于各种电子和光学器件的材料，最近重新引起了人们的关注。然而，由于多晶锗薄膜中缺陷诱导的受主密度高，其费米能级控制困难，限制了它们在上述器件中的应用。在此，我们通过显著调节多晶锗层的结晶度和电学性质并研究它们之间的相关性，从实验上估计了受主缺陷的起源。我们提出的线性回归分析方法基于从空穴浓度的温度依赖性推导出受主能级及其密度，揭示了存在两种不同的受主能级。对晶粒尺寸和退火后处理对空穴浓度影响的系统分析表明，深受主能级（53 - 103毫电子伏）可能归因于位于晶界处的悬空键，而浅受主能级（< 15毫电子伏）可能归因于晶粒中的空位。因此，本研究提出了一种基于机器学习的模拟方法，该方法可广泛应用于物理性质分析，并能为理解和控制多晶锗薄膜中的受主缺陷提供见解。
