Ultrahigh-speed InP-based D- and E-mode MODFETs with ultra-short electrochemically-recessed gate contacts

Summary form only given. When the gate length L/sub g/ of modulation-doped field-effect transistors (MODFETs) is reduced to deep sub-0.1 /spl mu/m range in pursuit of higher speed, it is most important to simultaneously reduce the gate-to-channel separation. The resulting high aspect ratio alleviates both the reduction of transconductance g/sub m/ resulting from drain-induced barrier lowering and the shift of threshold voltage V/sub th/. While the former point is essential for ultrahigh-speed ICs, the latter is the key to implementing enhancement-mode MODFETs (E-MODFET). However, the high aspect ratio is difficult to attain due to the enlarged side etching of gate grooves during recess etching, which leads to higher parasitic resistance. The electrochemical etching provides a feasible and easy-to-perform technology to form deep and narrow gate grooves for ultrahigh-speed MODFETs.