HgCdTe薄膜的输运特性及其应力调控

窄禁带直接带隙半导体材料碲镉汞(Hg1–xCdxTe)是一种在红外探测与自旋轨道耦合效应基础研究方面都具有重要应用意义的材料.本文对单晶生长的体材料Hg0.851Cd0.149Te进行阳极氧化以形成表面反型层,将样品粘贴在压电陶瓷上减薄后进行磁输运测试,在压电陶瓷未加电压时观察到了明显的SdH振荡效应.对填充因子与磁场倒数进行线性拟合,获得样品反型层二维电子气的载流子浓度为ns=1.25×10^16m^-2.在不同磁场下,利用压电陶瓷对样品进行应力调控,观测到具有不同特征的现象,分析应是样品中存在二维电子气与体材料两个导电通道.零磁场下体材料主导的电阻的变化应来源于应力导致的带隙的改变;而高场下产生类振荡现象的原因应为应力导致的二维电子气能级的分裂.

Magnetotransport properties and stress control of HgCdTe thin film

In recent years, the research on topological materials, including topological insulator and topological semimetal, has received a lot of attention in condensed matter physics. HgCdTe, widely used in infrared detection, also holds huge potential in this field. It has been reported that the strained thin Hg0.865 Cd0.135 Te can realize topological insulator phase by using a CdZnTe substrate. However, the stress caused by changing substrate has great limitations. For example, the stress cannot be changed once the sample has been grown.Hence, we try to use a piezoceramics(PZT) instead to implement the stress and control the properties of HgCdTe. The main purpose of our experiment is to verify its validity. As is well known, the band structure of Hg1–x Cdx Te can be precisely controlled by changing the content of Cd. When x lies between 0 and 0.165,HgCdTe features an inverted band structure, which is the premise of realizing topological phase. In this work,an inversion layer is induced on a single crystal grown HgCdTe bulk material by anodic oxidation, whose content of Cd is confirmed to be 0.149 by using XRD. Then the sample is thinned and attached to a PZT,which the tuning of stress is realized by applying a voltage to. Ohmic contacts are realized by indium in van der Pauw configuration. All measurements are carried out by using an Oxford Instruments 4 He cryostat with magnetic field applied perpendicularly to the sample plane. At 1.5 K and zero voltage, an evident SdH oscillation is observed. By fitting the linear relationship between filling factor and the reciprocal of magnetic field, the concentration is obtained to be ns = 1.25 × 10^16 m^-2. Subsequently, we scan the voltage from 200 V to–200 V continuously in different magnetic fields. Two phenomena with different characteristics are observed. It is found that the resistance changes linearly with stress at zero field while an SdH oscillation-like behavior occurs at high field. We attribute such a difference to the existence of two conductive channels: one is the bulk material and the other is the two-dimensional electron gas. It is also noteworthy that the topological phase in our sample cannot be determined because the quantum Hall conductance is polluted by the conductance of bulk material. In conclusion, our results show that it is an effective way to use the PZT to tune the stress and this method can also be applied to the research of other materials.