"Gallium Nitride (GaN) materials exhibit a wide bandgap, elevated electron mobility, high breakdown electric fields, substantial output power capabilities, and excellent thermal stability. AlGaN/GaN high electron mobility transistors (HEMTs), leveraging GaN materials, are capable of operating at elevated voltages with minimal on-resistance and have emerged as a focal point of research in the domain of microwave power devices and circuits over the past decade."

Conventional AlGaN/GaN HEMTs are primarily depletion-mode devices (threshold voltage Vth < 0V). The need for a negative gate-on voltage makes the design of depletion-mode HEMTs more complex than enhancement-mode devices (Vth > 0V). Current methods to achieve enhancement include trench gate technology, p-GaN technology, gate fluorine ion implantation, and common-source common-gate cascode configurations. Etching a trench gate reduces the distance between the gate and channel, enhancing control over the channel and increasing the device's threshold voltage. The p-GaN technique maintains the original two-dimensional electron gas (2DEG) channel while providing high electron mobility that enhances transconductance. Both methods require high-quality GaN etching techniques. Low-damage etching of GaN trench gates can reduce gate leakage; simultaneously, selective low-damage etching of p-GaN minimizes 2DEG loss and improves output characteristics. Thus, achieving low-damage and precise depth control in GaN etching is a key challenge in fabricating GaN enhancement-mode HEMTs.

This report focuses on low-damage GaN trench etching and highly selective P-GaN etching technologies, introducing their fundamental principles, optimization methods, and final results from various technical perspectives and applications, with the aim of positively impacting subsequent device fabrication processes and performance.