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

• Published in: IEEE electron device letters 2022-10, Vol.43 (10), p.1629-1632
• Main Authors: Yang, Tsung-Ying, Huang, Huuan-Yao, Liang, Yan-Kui, Wu, Jui-Sheng, Kuo, Mei-Yan, Chang, Kuan-Pang, Hsu, Heng-Tung, Chang, Edward-Yi
• Format: Article
• Language: English
• Subjects: AlGaN/GaN; Aluminum gallium nitride; Atomic layer etching; charge trap gate stack; Contact resistance; enhancement-mode; Etching; Ferroelectricity; Gallium nitrides; HEMTs; High electron mobility transistors; Logic gates; Performance evaluation; Plasmas; Semiconductor devices; Threshold voltage; threshold voltage uniformity; Wide band gap semiconductors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2022.3201900

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 \text {V}_{\text {th}} 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 ( \text {V}_{\text {th}} ) of 5.06 V, high maximum drain current ( \text {I}_{\text {D,MAX}} ) of 772 mA/mm with low on-resistance ( \text {R}_{\text {on}} ) of 8.57~\Omega \cdot \text {mm} and high breakdown voltage (BV) of 888 V, the device also showed good \text {V}_{\text {th}} uniformity. Finally, the contact resistance ( \text {R}_{\text {c}} ) was reduced from 0.46~\Omega \cdot \text {mm} to 0.15~\Omega \cdot \text {mm} by the ALE process, and the dynamic on-resistance (dyn- \text {R}_{\text {on}} ) was improved at the same time.