Excellent Responsivity and Low Dark Current Obtained With Metal-Assisted Chemical Etched Si Photodiode

Abstract

Metal-assisted chemical etched (MACE; also known as MacEtch or MCCE) nanostructures are utilized widely in the solar cell industry due to their excellent optical properties combined with a simple and cost-efficient fabrication process. The photodetection community, on the other hand, has not shown much interest toward MACE due to its drawbacks, including insufficient surface passivation, increased junction recombination, and possible metal contamination, which are especially detrimental to p-n photodiodes. Here, we aim to change this by demonstrating how to fabricate high-performance MACE p-n photodiodes with above 90% external quantum efficiency (EQE) without external bias voltage at 200-1000 nm and dark current less than 3 nA/cm 2 at −5 V using industrially applicable methods. The key is to utilize an induced junction created by an atomic layer deposited (ALD) highly charged Al 2 O 3 thin film that simultaneously provides efficient field-effect passivation and full conformality over the MACE nanostructures. Achieving close to ideal performance demonstrates the vast potential of MACE nanostructures in the fabrication of high-performance low-cost p-n photodiodes.

Boron-Implanted Black Silicon Photodiode with Close-to-Ideal Responsivity from 200 to 1000 nm

“…The most important photodiode parameters were characterized from the finished devices. EQE was measured between 200 and 1100 nm with a 10 nm interval at zero bias, with measurement details described in ref . Spectral responsivity ( R λ ) was calculated from the EQE with R λ = EQE q λ h c where q is the elementary charge, λ is the wavelength of light, h is the Planck constant, and c is the speed of light.…”

CMOS Image Sensor for Broad Spectral Range with >90% Quantum Efficiency

“…These methods have already been utilized to reduce the reflectance in solar cells and photodiodes. [11,12,[18][19][20] Evidently, b-Si could also be employed in image sensors to significantly improve the QE and broaden their photosensitive spectrum. Furthermore, there are indications that b-Si can also increase the optical path length in silicon by scattering the light, which could in turn enhance absorption and consequently improve the QE at NIR wavelengths.…”