Esendag Volkan, Feng Peng, Zhu Chenqi, Ni Rongzi, Bai Jie, Wang Tao
Department of Electrical and Electronic Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
Materials (Basel). 2022 Sep 1;15(17):6043. doi: 10.3390/ma15176043.
An extensive study has been conducted on a series of AlGaN/GaN high electron mobility transistor (HEMT) samples using metalorganic vapour phase epitaxy, to investigate the influence of growth modes for GaN buffer layers on device performance. The unintentional doping concentration and screw dislocation density are significantly lower in the samples grown with our special two-dimensional (2D) growth approach, compared to a widely-used two-step method combining the 2D and 3D growth. The GaN buffer layers grown by the 2D growth approach have achieved an unintentional doping density of 2 × 10 cm, two orders lower than 10 cm of the GaN samples grown using a conventional two-step method. High-frequency capacitance measurements show that the samples with lower unintentional doping densities have lower buffer leakage and higher breakdown limits. This series of samples have attained sub-nA/mm leakages, a high breakdown limit of 2.5 MV/cm, and a saturation current density of about 1.1 A/mm. It indicates that our special 2D growth approach can effectively lessen the unintentional doping in GaN buffer layers, leading to low buffer leakage and high breakdown limits of GaN/AlGaN HEMTs.
利用金属有机气相外延技术对一系列AlGaN/GaN高电子迁移率晶体管（HEMT）样品进行了广泛研究，以研究GaN缓冲层生长模式对器件性能的影响。与广泛使用的结合二维（2D）和三维（3D）生长的两步法相比，采用我们特殊的二维生长方法生长的样品中无意掺杂浓度和螺旋位错密度显著更低。通过二维生长方法生长的GaN缓冲层实现了2×10¹⁷cm⁻³的无意掺杂密度，比使用传统两步法生长的GaN样品的10¹⁹cm⁻³低两个数量级。高频电容测量表明，无意掺杂密度较低的样品具有较低的缓冲层泄漏和较高的击穿极限。这一系列样品实现了亚纳安/毫米的泄漏电流、2.5 MV/cm的高击穿极限和约1.1 A/mm的饱和电流密度。这表明我们特殊的二维生长方法可以有效减少GaN缓冲层中的无意掺杂，从而实现GaN/AlGaN HEMT的低缓冲层泄漏和高击穿极限。
