AlGaN/GaN HEMT Optimization Using the RoundHEMT Technology

The electrical characterization of epitaxially grown HEMT layer systems for device fabrication is commonly performed by Hall measurements. However, the ultimate characterization of a HEMT layer system is the transistor device itself. The RoundHEMT concept meets the need for a device technology with few fabrication steps that allows a fast feedback to epitaxy while providing an evaluation of important electrical and also processing data. Even though nearly identical Hall data on structures with different thickness and doping concentration of the AlGaN layers suggest similar device properties, the RoundHEMTs resolve remarkable differences in device performance. The best layer structure was used to fabricate HEMTs with IDS = 700 mA/mm, fT = 35 GHz, and fmax = 70 GHz for LG = 0.2 μm.