Laser-microstructured ZnO/p-Si photodetector with enhanced and broadband responsivity across the UV-Vis-NIR

TL;DR

This paper presents a novel ZnO/p-Si photodetector with laser-microstructured silicon that exhibits high sensitivity and broadband responsivity across UV, visible, and near-infrared wavelengths, achieved through atomic layer deposition and surface microstructuring.

Contribution

The study introduces a laser-microstructured silicon substrate combined with ALD-deposited ZnO, resulting in enhanced broadband photodetector performance with high crystalline quality and increased surface area.

Findings

Enhanced responsivity across UV-Vis-NIR spectrum.

Higher photocurrent in microstructured devices compared to planar.

Photodetectors operate effectively even below silicon bandgap.

Abstract

We develop ZnO/p-Si photodetectors by atomic layer deposition (ALD) of ZnO thin films on laser-microstructured silicon and we investigate their electrical and optical behavior, demonstrating high sensitivity and broadband operation. Microstructured p-type silicon was obtained by ns-laser irradiation in SF6 gas, which results in the formation of quasi-ordered and uniform microspikes on the silicon surface. The irradiated silicon contains sulfur impurities, which extend its absorbance to the near infrared. A thin film of ZnO was conformally deposited on the microstructured silicon substrates by ALD. Photoluminescence measurements indicate high crystalline quality of the ZnO film after annealing. Current-voltage (I-V) measurements of the ZnO/p-Si heterodiodes in dark show a non-linear behavior with unusual high current values in reverse bias. Under illumination photocurrent is observed for reverse bias, even for wavelengths below the silicon bandgap in the case of the laser-microstructured photodetectors. Higher current values are measured for the microstructured photodetectors, compared to planar ones. Photoconductivity measurements show enhanced responsivity across the UV-Vis-NIR spectral range for the laser-microstructured devices, due to their increased surface area and light absorption.