High Linearity and Low Noise Au-Free Ohmic Contact AlGaN/GaN HEMT Using Patterned Ohmic Recess for Ka-Band Applications

In this study, patterned ohmic recessed AlGaN/GaN high-electron mobility transistors (HEMT) with Au-free ohmic contact metal stack of Ti/Al/Ti/W was developed, and its linearity and microwave noise performance were analyzed for Ka-band application. Under the frequency of 28 GHz, the proposed Au-free ohmic contact device was measured with third output intercept point (OIP3) of 38.95 dBm and minimum noise figure (NFmin) of 1.80 dB. Compared to Au-based device, the proposed Au-free AlGaN/GaN HEMT exhibited superior linearity, which could be attributed to the lowered thermal budget of Au-free ohmic contact. Besides, the Au-free device had slightly inferior but still comparable DC and noise characteristics compared to conventional Au-based device, which could be attributed to the compensation posed by the patterned ohmic recess process. The results showed great potential of Au-free ohmic contact AlGaN/GaN HEMT to be used in high linearity transceiver for Ka-band applications.