Impact of SF6 Plasma on DC and Microwave Performance of AIGaN/GaN HEMT Structures

The improved dc and microwave properties of 2 mum gate length AlGaN/GaN based HEMT structures were observed after applying of a novel approach in the forming of the Schottky gate interface. The new approach uses a shallow recess-gate plasma etching of AlGaN barrier layer in combination with "in-situ" SF₆ surface plasma treatment under Schottky gate. A significant improvement in both the current gain cut-off frequency (f_t) and maximum oscillation frequency (f_max) were demonstrated. The exact mechanism to explain the improved performance of the SF₆ plasma treated HEMTs is in progress. A great potential of the approach for sub-micrometer gate length technology of HEMTs is also emphasized.