In-situ SiN combined with etch-stop barrier structure for high-frequency AlGaN/GaN HEMT

The etch-stop structure including the in-situ SiN and AlGaN/GaN barrier is proposed for high frequency applications. The etch-stop process is realized by placing an in-situ SiN layer on the top of the thin AlGaN barrier. F-based etching can be self-terminated after removing SiN, leaving the AlGaN barrier in the gate region. With this in-situ SiN and thin barrier etch-stop structure, the short channel effect can be suppressed, meanwhile achieving highly precisely controlled and low damage etching process. The device shows a maximum drain current of 1022 mA/mm, a peak transconductance of 459 mS/mm, and a maximum oscillation frequency (f_max) of 248 GHz.