Fabrication of E-mode AlGaN/GaN HEMT
Ray Hua/Horng1*, Chih-Tung/Yeh1
1Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung, Taiwan
* presenting author:Ray Hua Horng, email:huahorng@nchu.edu.tw
Up to date, a conventional method to fabricate enhnced-mode (E-mode) AlGaN/GaNHEMT, the so-called “recessed” technique, is to etch the epitaxy layer which underneath gate metal region. However, this kind of technique is mostly reached by dry etching which will cause lots of surface damage.
In our work, we used CF4 plsama treatment to fabricate E-mode HEMT which threshold voltage is higher than 2 V. Accroding to the measurement by transmission electron microscopy, the surface of epitaxy layer was not etched and damaged. In addition, the fluorine ions were indeed doped into semiconductor which was confirmed by secondary ion mass spectrometer. The structure of E-mode AlGaN/GaN HEMT was 3-μm gate and 2 side field plates that were 1 μm and 3μm, respectively. The device exhibited a maximum drain saturation current of 210 mA/mm, a peak gm of 44.1 mS/mm. Futthermore, low OFF-state gate leakage current of 10-6 mA/mm, ION/IOFF ratio is about 108 and high breakdown voltage of 1480 V were also demonstrated.

Keywords: Enhnced-mode AlGaN/GaN HEMT, Recessed, Threshold voltage