Sub-micron 3-D Electric Field Mapping in GaN Electronic Devices

AlGaN/GaN高电子迁移率晶体管（hemt）是高功率密度射频应用的变革性技术，包括雷达，卫星和移动通信。此外，基于GaN器件的高效电力转换系统是低碳经济的关键使能技术，包括可再生能源发电和交通电气化。然而，它们的全部潜力尚未实现，因为性能降低，以确保稳定的长期设备运行。这些器件中的电场分布的实验特征一直缺乏，尽管被确定为降解现象的主要驱动因素，包括击穿，电荷捕获和自加热。这些过程发生在器件通道内和周围，特别是栅极和场板下的亚微米区域，电场峰值位于该区域。本提案的目的是通过开发具有纳米尺度空间分辨率的光学三维（3-D）器件分析技术，逐步改变半导体器件的电场成像。主要的焦点将是电场诱导二次谐波产生（EFISHG）与固体浸没透镜（SILs）相结合。这将使我们能够研究关键的性能和可靠性挑战，包括(i)缓冲掺杂对器件层中电荷动态分布的影响，这会导致不良的记忆效应，（ii）优化场板几何形状以管理峰值电场，（iii）比较RF和DC操作期间的电场分布以改进可靠性预测。这些都是实现高性能可靠的GaN HEMT器件技术的关键途径，该技术充分利用了GaN材料特性的优势。

AlGaN/GaN high electron mobility transistors (HEMTs) are a transformative technology for high-power density radio frequency applications, including radar, satellite and mobile communications. In addition, efficient power conversion systems based on GaN devices are a key enabling technology for the low carbon economy, including renewable energy generation and transport electrification. However, their full potential has not yet been realised because performance is de-rated to ensure stable long-term device operation. Experimental characterisation of the electric field distribution in these devices has been lacking, despite being identified as a primary driver of degradation phenomena including breakdown, charge trapping and self-heating. These processes occur in and around the device channel and particularly the sub-micron region under the gate and field plate where peak electric fields are located. The aim of this proposal is a step-change in electric field imaging of semiconductor devices, by developing an optical three dimensional (3-D) device analysis technique with nanometre-scale spatial resolution. The primary focus will be on electric field induced second harmonic generation (EFISHG) combined with solid immersion lenses (SILs). This will enable us to investigate key performance and reliability challenges including (i) the effect of buffer doping on the dynamic distribution of charge in the device layers which causes an undesirable memory effect, (ii) optimization of field plate geometry to manage peak electric fields, (iii) comparing electric field distributions during RF and DC operation to improve reliability forecasts. These are on the critical pathway to achieving a high performance reliable GaN HEMT device technology which exploits the full benefits of the material properties of GaN.