Characterization of AlGaN/GaN HEMTs on 4-inch SiC substrate at Cryogenic temperature

We present the systematic analysis of DC and carrier transport behavior of AlGaN/GaN HEMTs in room-temperature and Cryogenic temperature. The fabricated L_g = 2 μm devices shows maximum-transconductance (g_{m_max}) of 175 mS/mm and off-current (I_off) of 10 μA/mm in comprision to g_{m_max} of 298 mS/mm and I_off of 1 nA/mm. Also, series resistance (R_S) is improved from 1.8 Ω∙mm at 300 K to 0.44 Ω∙mm at 4 K due to reduction of sheet resistance of access region. Carrier transport at 300 K and 4 K were evaluated through gm modeling, indicating that improvement of effective mobility (μ_{n_eff}) and slightly improvement of saturation velocity (v_sat). Here, we investigate AlGaN/GaN HEMTs behavior in Cryogenic temperature applications such as deep space reception, radio astronomy, and quantum computing.