The design and fabrication of monolithic millimeter wave optical receivers

The optical receiver circuits were fabricated monolithically on GaAs based materials. The optical receivers were to detect the modulated signal at 44 GHz transmitted through optical carrier. MSM photodetectors and P-MODFET's were employed in the receiver circuits. The photodetector layer was specially designed for the high quantum efficiency for 770 nm light by using Bragg reflector layers and cap layer. InGaAs channel P-MODFET's, adapted for the post-detection amplifiers, exhibited f/sub t/ of 90 GHz and f/sub max/ of 100 GHz. For DC bias lines and isolations, ground plane capacitors and thin film isolated bias lines were used. The circuit was designed and fabricated by conjugately matching the S-parameters of each device at 44 GHz through CPW transmission lines. The receivers were measured up to 40 GHz, showing about 3 dB gain at 39 GHz.