Improved frequency performance in AlGaN/GaN HEMTs on Si using hydrogen silsesquioxane-assisted gate

AlGaN/GaN HEMTs have been regarded as the most promising option for achieving high-frequency power amplifier in various applications, including wireless communication, aerospace, and radar systems. To enable their use at even higher frequency, we conducted a study to enhance the frequency characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) on a silicon substrate. By employing a hydrogen silsesquioxane (HSQ)-assisted gate, AlGaN/GaN HEMT with an L_G of 0.17 μm and L_SD of 5 μm exhibited a V_TH of 4.5 V, I_D.max of 885 mA/mm, and g_m.max of 253 mS/mm. The planar-gate without HSQ shows V_TH of 4.4 V, I_D.max of 876 mA/mm, and g_m.max of 258 mS/mm. The DC characteristics are comparable to those observed in planar-gate HEMT with a conventional gate structure. Though the DC characteristics of both devices are similar, the HSQ-assisted gate HEMT exhibits a higher f_T/f_max of 55/89 GHz, whereas the planar-gate HEMT yields an f_T/f_max of 38/64 GHz. The 32% reduction in the total extrinsic gate capacitance (C_gs + C_gd) is the major contributor to the improved frequency performance of the HSQ-assisted gate AlGaN/GaN HEMT. The adoption of HSQ-assisted gate AlGaN/GaN HEMTs presents itself as a highly advantageous choice for achieving higher-frequency operations.