Planar integration of a resonant-tunneling diode with pHEMT using a novel proton implantation technique

A novel technique of integrating resonant-tunneling diodes (RTDs) with pseudomorphic high-electron-mobility transistors (pHEMTs) is demonstrated. A proton was implanted through the pHEMT layers to convert the RTD structure underneath to a high-resistivity buffer without degrading the performance of the pHEMT. The cutoff frequency is 16 GHz for a 1.5-/spl mu/m-gate-length pHEMT on such an implanted buffer. Substituting the conventional deep mesa etch with ion implantation maintains a highly planar surface. Such a monolithically integrated RTD/pHEMT oscillator is described.