Au-Free AlGaN/GaN HEMT on Flexible Kapton Substrate

• Published in: IEEE transactions on electron devices Vol. 69; no. 8; pp. 4212 - 4217
• Main Authors: Niranjan, S, Muralidharan, R., Sen, Prosenjit, Nath, Digbijoy N.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AlGaN/GaN high-electron mobility transistors (HEMT); Aluminum gallium nitride; Aluminum gallium nitrides; Au-free process; Carrier density; CMOS compatibility; Electrical resistivity; flexible electronics; Gallium nitrides; HEMTs; High electron mobility transistors; Kapton; Kapton (trademark); Logic gates; Performance evaluation; Polyimide resins; Radius of curvature; Reduction; Semiconductor devices; Silicon; Substrates; Thermal conductivity; Wide band gap semiconductors
• DOI: 10.1109/TED.2022.3186267
• ISSN: 0018-9383

In this article, we report on the electrical performance of AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated using gold (Au)-free process, after being transferred onto flexible Kapton tape. The transfer process followed in this work can be easily scaled-up to wafer level and involves a relatively simple process of epoxy bonding of the thin device layer onto the Kapton substrate. Electrical characteristics of the flexible HEMT indicate 5%-10% higher ON-current when bent with a radius of curvature of 2.1 cm (at low drain bias voltages), while the OFF-state performance remains unaffected. Initially, 2-DEG properties such as field-effect mobility and carrier concentration have been extracted. While FATFET measurements indicate negligible change in field-effect mobility, <inline-formula> <tex-math notation="LaTeX">{C} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">{V} </tex-math></inline-formula> measurements indicate <inline-formula> <tex-math notation="LaTeX">\sim 10 </tex-math></inline-formula>% reduction in 2-DEG concentration after transfer. The comparison of the electrical characteristics of Au-free HEMTs indicates <inline-formula> <tex-math notation="LaTeX">\sim 50 </tex-math></inline-formula>% reduction in the ON-current of the transferred devices. This is attributed to heating of the transistor channel caused due to low thermal conductivity of the polymer Kapton tape. Electrical characteristics of the flexible HEMT carried out under drain pulsing further support the above observation. This work is among one of the few reports on Au-free AlGaN/GaN HEMT operation on flexible Kapton tape.