Electric fields drive the degradation of wide-bandgap semiconductor devices. However, directly mapping the electric field inside an active device region remains challenging. Here we show that electric-field-induced second harmonic generation can be used to map the electric field in the device channel of GaN-based high-electron-mobility transistors at submicrometre resolution. To illustrate the capabilities of the approach, we use it to examine the impact of carbon impurities in the epitaxial buffer layer of a device. Carbon is a p dopant in GaN, and small changes in its concentration can dramatically change the bulk Fermi level, sometimes resulting in a floating buffer that is ‘short-circuited’ to the device channel via dislocations. Our measurements show that very different electric field distributions can occur in devices with different carbon concentrations, despite them having similar device terminal characteristics. We also show that dislocation-related leakage paths can lead to inhomogeneity in the electric field.

电场驱动宽带隙半导体器件的退化。然而，直接映射有源器件区域内的电场仍然具有挑战性。在这里，我们展示了电场诱导的二次谐波产生可用于在亚微米分辨率下映射基于 GaN 的高电子迁移率晶体管的器件通道中的电场。为了说明该方法的功能，我们使用它来检查碳杂质对器件外延缓冲层的影响。碳是 GaN 中的 ap 掺杂剂，其浓度的微小变化可以显着改变体费米能级，有时会导致浮动缓冲层通过位错“短路”到器件沟道。我们的测量表明，具有不同碳浓度的设备中可能会出现非常不同的电场分布，尽管它们具有相似的设备终端特性。我们还表明，与位错相关的泄漏路径会导致电场的不均匀性。