A Normally-Off GaN MIS-HEMT Fabricated Using Atomic Layer Etching to Improve Device Performance Uniformity for High Power Applications

Normally-off ferroelectric charge trap gate stack GaN high electron mobility transistor (FEG-HEMT) was fabricated with atomic layer etching (ALE) to precisely control the device parameters including Vth of the device. The ALE process consists of cyclic Cl2 adsorption modification steps and the Ar ion removal steps. The ALE process achieved etch-per-cycle (EPC) of 0.347 nm/cycle and superior etching morphology with RMS =0.281 nm. The fabricated GaN HEMT using the ALE process exhibited a high threshold voltage (Vth ) of 5.06 V, high maximum drain current (I D,MAX) of 772 mA/mm with low on-resistance (Ron) of 8.57∼\Ω mm and high breakdown voltage (BV) of 888 V, the device also showed good Vth uniformity. Finally, the contact resistance (Rc) was reduced from 0.46∼\Ω \mm to 0.15∼\Ω \mm by the ALE process, and the dynamic on-resistance (dyn- Ron) was improved at the same time.