A novel 3-D integrated HFET/RTD frequency multiplier

A merged heterostructure field-effect transistor/resonant tunneling diode (HFET/RTD) combination is proposed to act as a (sub)millimeter wave source via highly efficient frequency multiplication and its functionality is demonstrated at intermediate frequency. On a semi-insulating InP-substrate a HFET followed by a double barrier RTD-layer sequence is grown in a single molecular beam epitaxy (MBE)-run. A novel monolithic frequency multiplier circuitry is developed where the RTD is used as load in contrast to other concepts where the RTD is inserted in the input of a three-terminal device. The resulting output voltage is rectangular type and rich in higher odd harmonics. This approach avoids classical disadvantages of the RTD because biasing in the negative-differential-regime is not required and bistability of the I-V-characteristic is used rather than the negative differential resistance. The small signal parameters of the single devices realized with optical lithography, wet etching, and self-aligned process technology are used as input data for a microwave design software (MDS) and the frequency multiplication is modeled up to submillimeter wave frequencies.