A 0.4-4 THz p-i-n Diode Frequency Multiplier in 90-nm SiGe BiCMOS

This article introduces a silicon-based source that can radiate power from the lower end of the terahertz (THz) spectrum into the far-infrared region. The radiator consists of a millimeter-wave (mm-wave) oscillator that drives a PIN diode multiplier. The p-i-n diodes exhibit reverse recovery when driven strongly, and the diode switches a large amount of current in a short interval. This process is highly non-linear and generates a harmonic-rich waveform, which is utilized here for higher harmonic generation. An on-chip folded dipole antenna is used to radiate the generated THz signal. The harmonic radiation properties of the folded dipole are analyzed and presented here. Wireless harmonic injection locking is also demonstrated in this work in order to synchronize the chip to an external source. Designed in GlobalFoundries 90-nm SiGe BiCMOS process, the chip has an effective isotropic radiated power (EIRP) of 13 dBm and −14.2-dBm radiated power at 0.39 THz. The chip is characterized up to 0.8 THz using Virginia Diodes (VDI) mixers, and an EIRP of −3.8 dBm is measured at 0.78 THz. In order to measure the radiated tones at higher frequencies, Fourier-transform infrared (FTIR) spectroscopy is used with a room-temperature deuterated triglycine sulfate (DTGS) detector. Measurement results confirm the presence of tones extending from the THz region into the far-infrared region, with an SNR of 18.4, 14, 9.3, and 6.7 dB at 1.17, 2.21, 3.25, and 4.03 THz, respectively. This work is the first demonstration of a silicon source capable of generating detectable tones at far-infrared frequencies.