PhD Defence Notice: "III-V Semiconductor Nanowire Avalanche Photodiodes" by Burak Tekcan

Candidate: Burak Tekcan
Title: III-V Semiconductor Nanowire Avalanche Photodiodes
Date: December 9, 2022
Time: 10:00 AM
Place: EIT 3141
Supervisor(s): Ban, Dayan - Reimer, Michael

Abstract:
Detecting single photons with high efficiency and timing resolution opens up new possibilities for various technologies such as light detection and ranging (LIDAR), ultra-long distance communications, singlet oxygen detection for cancer treatment, optical coherence tomography (OCT) and quantum information. The image quality in a spectroscopy system for analysis of biological tissue or precision of LIDAR systems can be significantly improved with quantum sensing technologies. Moreover, OCT imaging systems can be improved for higher resolution mapping of human retina leading to early detection of blinding diseases. Detecting single photons can also enable high speed quantum communication technologies by improving the detection speed.

Currently, the two leading technologies for quantum detection are superconducting nanowires and semiconductor avalanche photodiodes. Superconducting nanowires have excellent detection efficiencies (>90%) and precise timing resolution (<50 ps); however, they require cryogenic temperatures and bulky compressors and pumps to operate (typically <4K), which results in a huge limitation for practical and portable applications. In contrast, semiconductor based single photon avalanche diode (SPAD) technology exists for portable applications, nonetheless, the high efficiency is achieved for a small wavelength range and at the cost of timing resolution (200-500 ps).

This work offers a novel approach to improve the quantum efficiency of semiconductor based photodiodes by taking advantage of remarkable optical and electrical properties of nanowires. Embedding photodiode architecture in nanowire arrays show great promise leading the way towards next generation quantum detectors. In this work, III-V semiconductor nanowire arrays exhibit near-unity absorption for an unprecedented wavelength range when the nanowire shape and geometry is optimized. Previously developed InP based nanowire quantum sensors exhibited single photon sensitivity and fast response with 0.6ns rise time and only 17ps timing jitter at room temperature.
 
In this thesis, the aim is to extend the single photon sensitivity towards near infrared and short-wave infrared wavelengths by using InGaAs as an active material. Our novel nanowire pin photodiodes based on InGaAs displayed remarkable improvement in quantum efficiency (>85%) including the wavelength band “valley of death” (800-1000nm) where OCT imaging operates for enhanced sensitivity and axial resolution for eye imaging. We also built nanowire based avalanche photodiodes to introduce gain mechanism detecting single photons efficiently at short wave infrared. The thesis describes the approach to design nanowire arrays for near unity absorption, the process to fabricate those structures in a cleanroom and electrical and optical characterization of fabricated nanowire arrays demonstrating high quantum efficiency and fast response.