Wuhan National Laboratory for Optoelectronics (WNLO), Huazhong University of Science and Technology (HUST), Wuhan, 430074, China.
School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074, China.
Sci Rep. 2018 Jan 11;8(1):486. doi: 10.1038/s41598-017-18964-w.
The tunable disorder of vacancies upon annealing is an important character of crystalline phase-change material GeSbTe (GST). A variety of resistance states caused by different degrees of disorder can lead to the development of multilevel memory devices, which could bring a revolution to the memory industry by significantly increasing the storage density and inspiring the neuromorphic computing. This work focuses on the study of disorder-induced carrier localization which could result in multiple resistance levels of crystalline GST. To analyze the effect of carrier localization on multiple resistant levels, the intrinsic field effect (the change in surface conductance with an applied transverse electric field) of crystalline GST was measured, in which GST films were annealed at different temperatures. The field effect measurement is an important complement to conventional transport measurement techniques. The field effect mobility was acquired and showed temperature activation, a hallmark of carrier localization. Based on the relationship between field effect mobility and annealing temperature, we demonstrate that the annealing shifts the mobility edge towards the valence-band edge, delocalizing more carriers. The insight of carrier transport in multilevel crystalline states is of fundamental relevance for the development of multilevel phase change data storage.
空位在退火过程中的可调无序是晶态相变材料 GeSbTe（GST）的一个重要特性。不同程度无序引起的多种电阻状态可导致多级存储器件的发展，这可能通过显著增加存储密度和激发神经形态计算为存储行业带来革命性变化。这项工作专注于研究空位诱导的载流子局域化，这可能导致晶态 GST 的多个电阻水平。为了分析载流子局域化对多个电阻水平的影响，我们测量了晶态 GST 的本征场效应（施加横向电场时表面电导率的变化），其中 GST 薄膜在不同温度下退火。场效应测量是对传统输运测量技术的重要补充。我们获得了场效应迁移率，并显示出温度激活，这是载流子局域化的标志。基于场效应迁移率与退火温度之间的关系，我们证明退火将迁移率边缘推向价带边缘，使更多的载流子去局域化。在多级晶态中载流子输运的洞察力对于多级相变数据存储的发展具有重要的基础性意义。
