On-Chip Photonic THz Emitter with Integrated InGaAs UTC-PD and 2×2 MPA Array on SiC Substrate

This work presents an on-chip integration of a 2×2 microstrip patch antenna (MPA) array with an InGaAs uni-traveling-carrier photodiode (UTC-PD) on a silicon carbide (SiC) substrate, aimed at enhancing the output capability of photonic THz sources. The absolute output power of an individual InGaAs UTC-PD was enhanced using a high-thermal-conductivity SiC substrate via flip-wafer bonding technique, while the MPA array improved relative power efficiency by optimizing radiation pattern in the broadside direction. Measurements demonstrated that the use of SiC contributed to an increase in the UTC-PD’s saturation photocurrent to 10 mA and confirmed significant gains in the 270 GHz band, along with a 3 dB bandwidth of 10 GHz. E-field radiation patterns at 270 GHz and 300 GHz demonstrated excellent directivity with a narrowed beamwidth of 60°. These results highlight the array’s directional emission capabilities and its potential for compact, high-performance on-chip THz emitters, paving the way for future wireless THz applications.