Self-aligned process for forming microlenses at the tips of vertical silicon nanowires by atomic layer deposition

TL;DR

This paper presents a novel self-aligned atomic layer deposition process to fabricate microlenses on silicon nanowires, enabling precise, scalable, and efficient light coupling in optoelectronic devices.

Contribution

A new self-aligned ALD technique for forming microlenses on silicon nanowires with size control and enhanced optical properties.

Findings

Microlenses are centered on nanowires due to the process.

The microlens size is self-limited by nanowire spacing.

Simulations show improved light absorption in silicon nanostructures.

Abstract

The microlens is a key enabling technology in optoelectronics, permitting light to be efficiently coupled to and from devices such as image sensors and light-emitting diodes. Their ubiquitous nature motivates the development of new fabrication techniques, since existing methods face challenges as microlenses are scaled to smaller dimensions. Here, we demonstrate the formation of microlenses at the tips of vertically-oriented silicon nanowires via a rapid atomic layer deposition (ALD) process. The nature of the process is such that the microlenses are centered on the nanowires, and there is a self-limiting effect on the final sizes of the microlenses arising from the nanowire spacing. Finite difference time domain electromagnetic simulations are performed of microlens focusing properties, including showing their ability to enhance visible-wavelength absorption in silicon nanostructures.