Demonstration of Normally-Off N-Polar GaN Deep Recess HEMT

In this letter, we report the first normally-off N-polar GaN deep recess high electron mobility transistor (HEMT). Utilizing atomic layer etching (ALE), followed by acid treatment, we achieved normally-off operation through gate recess etching on an N-polar GaN deep recess HEMT epitaxial structure, with metal-organic chemical vapor deposition (MOCVD) SiN x serving as the gate insulator. A threshold voltage of + 0.5 V was attained, along with impressive metrics, such as low off-state drain leakage current (12 nA/mm), off-state gate leakage current (28 nA/mm), and on-state gate current (35 nA/mm). Remarkable performance parameters include a high on/off ratio of 5 x 10(7) , drain off-state breakdown voltage of 53 V, and gate forward bias breakdown voltage of 5 V. Small signal measurements demonstrated a current-gain cutoff frequency (f(T)) and power-gain cutoff frequency (f(MAX)) of 8.6 and 52.1 GHz, respectively, with a gate length of 0.6 mu m. Furthermore, a competitive output power density of 5.1 W/mm with 50% power added efficiency was achieved at 4 GHz. Results underscore the potential of normally-off N-polar GaN deep recess HEMTs for both RF and high-voltage applications.