Transfer-Substrate Process for InP RTD-Oscillator Characterization

THz oscillators with on-chip antennas containing no ground plane are affected by substrate modes and therefore undirected radiation into free space. When integrating such antennas with focusing lenses, accurate sub-μm alignment is required. This work presents an assembly process utilizing an HRFZ-Si transfer substrate between the InP RTD chip and a hyper-hemispherical silicon lens, enabling precise alignment. We developed a bonding process for 1.2 × 1.2 mm
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InP RTD chips with an optical adhesive utilizing an advanced sub-micron bonder. THz-TDS measurements of the HRFZ silicon wafer were carried out to analyze the losses within the created setup by EM simulations. The assembly process was verified with measurements of a 300 GHz triple barrier (TB)-RTD oscillator using an SBD detector.