Black-Silicon Ultraviolet Photodiodes Achieve External Quantum Efficiency above 130

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Current ultraviolet (UV) sensors exhibit suboptimal performance across diverse applications, including spectroscopy, biotechnology, and industrial process control.
• Existing UV sensor technology is limited by the fundamental one-photon-one-electron interaction, capping external quantum efficiency (EQE) at 100%.

Purpose of the Study:

• To demonstrate a novel photodetector design that surpasses the theoretical EQE limit for UV sensing.
• To investigate the underlying physical mechanisms responsible for achieving ultra-high quantum efficiencies in UV sensors.

Main Methods:

• Fabrication of a nanostructured silicon photodiode featuring a self-induced junction.
• Characterization of the photodiode's performance, including certified external quantum efficiency measurements in the UV spectrum.
• Analysis of carrier generation dynamics, specifically focusing on impact ionization within the nanostructures.

Main Results:

• Achieved a certified external quantum efficiency exceeding 130% in the UV range without external amplification.
• Demonstrated that the enhanced efficiency stems from effective multiple carrier generation via impact ionization.
• Validated the nanostructured silicon photodiode design as a high-performance UV sensing solution.

Conclusions:

• The developed nanostructured silicon photodiode significantly advances UV sensor technology by breaking the one-photon-one-electron efficiency barrier.
• The underlying principle of multiple carrier generation through impact ionization offers a pathway to enhance photodetector efficiency beyond the Shockley-Queisser limit.
• The technological concept is adaptable to other semiconductor materials, potentially extending high-efficiency responses to longer wavelengths.