AlGaN/AlN/GaN结构中二维电子气的输运特性

The transport property of two dimensional electron gas in AlGaN/AlN/GaN structure

对使用金属有机物汽相沉积法生长的AlGaN/AlN/GaN结构进行的变温霍尔测量,测量结果指出在AlN/GaN界面处有二维电子气存在且迁移率和浓度在2K时分别达到了1.4×104cm2.V-1.s-1和9.3×1012cm-2,且在200K到2K范围内二维电子气的浓度基本不变,变磁场霍尔测量发现只有一种载流子(电子)参与导电.在2K温度下,观察到量子霍尔效应,Shubnikov-de Haas(SdH)振荡在磁场约为3T时出现,证明了此结构呈现了典型的二维电子气行为.通过实验数据对二维电子气散射过程的半定量分析,推出量子散射时间为0.23ps,比以往报道的AlGaN/GaN结构中的散射时间长,说明引入AlN层可以有效减小合金散射,进一步的推断分析发现低温下以小角度散射占主导地位.

Variable temperature Hall effect measurement was performed on the AlGaN/AlN/GaN structure with AlN interlayer grown on sapphire by metalorganic chemical vapor deposition. It was measured that the mobility and density of the two dimensional electron gas at the interface of AlN/GaN were 1.4 × 10^4 cm^2 · V^-1 · s^-1 and 9.3 ×10^12 cm^-2 at 2 K, respectively. Low temperature variable magnetic field measurement manifested that only a single type of carriers contributed to the conductivity in this structure. Quantum Hall effect was observed in field as low as 3 T at 2 K. The calculated quantum scattering time of 0.23 ps is longer than that of AlGaN/GaN structure. This improvement is attributed to the AlN interlayer which effectively reduces the scattering. In addition, further analysis revealed that the small-angle scattering was important in this structure.