High Performance Silicon Optoelectronic Devices Enabled by Photocarrier Transport-Recombination Engineering and Surface Light-Trapping Topologies

Photocarrier generation, transport, recombination and extraction are fundamental processes for modern semiconductor optoelectronic devices. The need for light-trapping strategies to enhance the overall optical absorption of semiconductor devices has inspired a wide variety of studies and applications. Consequently, understanding and effectively manipulating surface recombination and carrier transport within light-trapping-enhanced optoelectronic devices are critical for the attainment of high device performance and novel functionalities. In this thesis, in-depth exploration of photocarrier generation and recombination processes is conducted in various devices that integrate different micro-nano light-trapping structures.The studied devices include silicon Schottky photodiodes and heterojunction photodiodes. These devices are further enhanced via integration of excellent surface light trapping morphologies which include wave-interference photonic crystals and low-aspect-ratio ultra-high absorbing nanostructures. The advantages of photocarrier transport and recombination control are demonstrated through the realization of multi-functional photodetectors exhibiting superior performance. We first demonstrate atomically thin surface inversion layer at the oxide-silicon surface for low surface recombination and thus low noise photodetectors. Next, we employ the developed strategies to mitigate photocarrier surface recombination within a device with novel nanostructured black Si morphology to demonstrate broadband near-unity external quantum efficiency (EQE). The effect of the surface electric field on photocarrier extraction is further investigated by Haynes-Shockley experiment analogues, providing essential insights on photocarrier recombination/extraction for various semiconductor materials/devices. Further dual-interface band bending manipulation and photocarrier transport engineering are employed to demonstrate the viability of an identical photodiode to concurrently sense broadband and narrowband light. Additionally, we also show the integration of organic semiconductor (in contrast to inorganic semiconductors) high work-function contacts on wave-interference photonic crystals for faint nanowatt-level light detection. Further, we demonstrate that nanometer thin transparent contacts can collect nearly-all approaching surface photocarriers, paving a path to estimating the photogeneration of an arbitrary optical absorber by extracting measurable photocarriers. The results and discussions in this thesis provide key insights amenable to understanding and advancing efficacious photocarrier transport and collection in various semiconductor devices.

Department dc:contributor.department

Electrical and Computer Engineering

Year dc:date.issued

2023

Author dc:creator

• Zhang, Yibo

Advisor dc:contributor.advisor

• Kherani, Nazir P

Handle dc:identifier.uri

https://hdl.handle.net/1807/149767

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/149767