Silicon etched-groove permeable base transistors with 90-nm finger width

Silicon etched-groove permeable base transistors (PBTs) which utilize a new structure to eliminate surface depletion effects are discussed. The 90-nm-wide fingers are n/sup +/-doped, and the channel region is buried below the bottom of the grooves. Doping and thickness of the active layer were optimized using two-dimensional computer simulations. The maximum measured transconductance of 155 mS/mm is the highest reported for Si PBTs and demonstrates the potential of silicon as substrate material. The measured transit frequency was 12 GHz; f/sub max/ reached 13 GHz. It has been recognized that for improved high-frequency performance a reduction of the gate capacitance is necessary, demanding a more precise control of groove depth and geometry. >