High-Speed Photodiodes for Applications in Photonic-Based Millimeter Wave Systems

Technologies based on millimeter wave (mmWave) (30-300 GHz) systems continue to emerge in the areas of wireless communications, radar, imaging, and spectroscopy. While exact requirements vary between applications, a fundamental requirement exists for all photonic-based platforms: mmWave sources capable of high-frequency, high-power operation and, ideally, wide tunability. To achieve mmWave operation in photonic-based approaches, photodiodes (PDs) with broad bandwidth (DC to 100’s of GHz) and high-power capability play a critical role in converting optical signals into electrical signals.

This thesis demonstrates a push forward of the state-of-the-art in high-speed and high-power III-V based photodiodes for application in photonic-based mmWave systems. To this end, novel approaches to the epitaxial (semiconductor) design, microwave circuit design and integration, and methods of device fabrication are shown. Through the mmWave frequency range, flat roll-off at low -1 V bias, and high power for single device photodiodes is demonstrated. 3-dB bandwidths above 110 GHz under bias, and 92 GHz at zero bias are also achieved. Better than 70% yield of a photodiode array fabricated with a new surface normal PD fabrication procedure is also shown.