Design, fabrication, and optical characterization of one-dimensional photonic crystals based on porous silicon assisted by in-situ photoacoustics

Cristian Felipe Ramirez-Gutierrez,Harol David Martinez-Hernandez,Ivan Alonso Lujan-Cabrera,Mario Enrique Rodriguez-García

doi:10.1038/s41598-019-51200-1

Cristian Felipe Ramirez-Gutierrez, Harol David Martinez-Hernandez + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-51200-1

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Abstract

We present a methodology to fabricate one-dimensional porous silicon (PSi) photonic crystals in the visible range by controlled etching and monitored by photoacoustics. Photoacoustic can record in-situ information about changes in the optical path and chemical reaction as well as in temperature, refractive index, and roughness during porous layers formation. Radiometry imaging can determine the carrier distribution of c-Si substrate that is a fundamental parameter to obtain high-quality PSi films. An electrochemical cell was calibrated through a series of single PSi layers that allows knowing the PA amplitude period, porosity, and roughness as a function of the current density. Optical properties of single layers were determined using the reflectance response in the UV-Vis range to solve the inverse problem through genetic algorithms. PhC structures were designed using the transfer matrix method and effective media approximation.Based on the growth kinetics of PSi single layers, those structures were fabricated by electrochemical etching monitored and controlled by in-situ photoacoustics.

Highlights

Nowadays, groundbreaking sensors are based on photonic crystals (PhC)[1], porous materials[2], and bio-inspired structures that allow accurate and reliable measures through its optical and electrical response[3,4,5,6]
A common characteristic in the cited works is that the fabrication of the porous silicon (PSi) distributed Bragg reflector (DBR) always depends in using an arbitrary value of current density and etching time, resulting in a random optical response referred to the position of photonic band-gap, limited bandwidths, and low optical quality
The critical parameters that influence the PSi formation are the substrate quality, that is related to the carrier distribution along the wafer as was showed by www.nature.com/scientificreports photocarrier radiometry images as well as the control of the electrolyte composition and reaction temperature

Summary

Introduction

Nowadays, groundbreaking sensors are based on photonic crystals (PhC)[1], porous materials[2], and bio-inspired structures that allow accurate and reliable measures through its optical and electrical response[3,4,5,6]. A common characteristic in the cited works is that the fabrication of the PSi DBRs always depends in using an arbitrary value of current density and etching time, resulting in a random optical response referred to the position of photonic band-gap, limited bandwidths, and low optical quality. This means that before producing the PSi DBR there was not a previous design or control. PCR is a non-contact, non-intrusive, and non-destructive technique that has been used for mapping the implant dose across the c-Si wafers[45,46,47] as well as to determine the carrier distribution in p and n Si wafers[48]

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