Enhanced DC and RF characteristics in E/D-mode AlGaN/GaN HEMTs by TiN-based source contact technology

the DC and RF characteristics of Enhancement/Depletion (E/D)-mode AlGaN/GaN HEMTs using the TiN-based source ledge are deeply studied. As a method of reducing the source resistance, the TiN-base source ledge is very attractive for high performance E/D-mode device because the transconductance and small signal characteristic can be effectively improved in a wider range. With this technology, a better improvement of transconductance from 340mS/mm and 334mS/mm to 412mS/mm and 415mS/mm in E/D-mode device is observed. The third order extrinsic transconductance and the input third order intercept point (IIP3) are studied for its linearity performance as compared to the conventional device. The current collapse of E- and D-mode device with L_ledge =1$\mu$m have been suppressed only 3.41% and 3.9% of drain saturation current, respectively. The variation of current collapse with length of TiN-based ledge is monotonic both in E/D-mode device. Due to reduce the source resistance, the $f_{T}/f_{MAX}$ of 42/100GHz increase to the 57/118GHz for E-mode devices, and the $f_{T}/f_{MAX}$ of 50/71GHz increase to the 67/90GHz for D-mode devices respectively. A higher threshold voltage without sacrificing the $f_{T}$ value in E-mode device and a higher $f_{T}$ while keeping the better electrostatic control in D-mode device are obtained by TiN-based source ledge.