Abstract
Silicon photonics is a promising platform for applications in optical communication, sensing, and quantum computing, owing to its low-loss passive components, CMOS compatibility, and potential for photonic–electronic co-integration. However, a major challenge is the absence of a monolithic silicon-based laser source, due to the indirect bandgaps of Si and Ge. To overcome this limitation, heterogeneous integration of III–V materials with silicon has attracted significant research interest.
Although photonic integrated circuits (PICs) provide advantages such as low cost, compact footprint, and low propagation loss, Ge/Si-based photodetectors still underperform compared to their III–V counterparts, exhibiting lower responsivity, higher dark current, and limited opportunities for bandgap engineering. To address this, the modified uni-traveling carrier photodiode (MUTC), a critical component in PICs, is investigated for performance enhancement in terms of responsivity, bandwidth, and thermal power dissipation.
This research focuses on three key aspects:
1. Epitaxial structure optimization with varying thermal conductivities, supported by thermal modeling, to improve RF output power.
2. Bandgap engineering in III–V semiconductors to enhance the 3 dB bandwidth of compact photodiodes through electron velocity overshoot.
3. Design and optimization of heterogeneous MUTC photodiodes integrated with Si₃N₄ and Si waveguides using Lumerical simulations, followed by comprehensive electrical and optical characterization.
By improving MUTC photodiode performance across these areas, this work enables the development of integrated photonic systems capable of supporting high-power, high-speed applications.
