Vertical scaling of ultra-high-speed AlInAs-GaInAs HEMTs
The scaling of the vertical dimensions of 0.15-μm-gate-length Al0.48In0.52As-Ga0.47In0.53As high-electron-mobility transistors (HEMTs) to reduce their well-known excessive gate leakage current, premature breakdown voltage, and poor output conductance is discussed. It is found that, with a proper choice of doping densities and layer thicknesses, it is possible to realize very-high-performance AlInAs-GaInAs HEMTs (fT = 160 GHz, fmax = 300 GHz for 0.15-μm × 50-μm devices) with low gate leakage current, high breakdown voltage (7.0 V), and very low DC output conductance (45-mS/mm). The DC output conductance exhibits a very strong dependence on the AlInAs doping-thickness product and appears to be a limiting factor in the device power gain. By reducing the doping-thickness product, it was possible to reduce the output conductance by a factor of 3 and thus increase the power gain cutoff frequency by a factor of 1.7.
