# Spectroscopic Ellipsometry investigation on anisotropic optical properties of sputtered AlN films

## TL;DR

This study investigates the anisotropic optical properties of sputtered AlN films using spectroscopic ellipsometry, revealing their potential for deep-UV optoelectronic applications and how these properties evolve with growth temperature.

## Contribution

It provides detailed uniaxial optical constants of AlN films as a function of growth temperature, using spectroscopic ellipsometry combined with TEM and AFM validation.

## Key findings

- High n and low k at 210 nm for AlN grown at 400°C
- AlN films are transparent from NIR to 354 nm with band gaps 5.7-6.1 eV
- Highly oriented AlN exhibits small birefringence and dichroism near band edge

## Abstract

We report the uniaxial anisotropic optical constants of Wurtzite type AlN films deposited on Si (100) substrate using DC reactive magnetron sputtering as a function of growth temperature (Ts, 35 to 600 C). Evolution of optical properties with Ts is investigated by Spectroscopic Ellipsometry (SE) technique. Thickness and roughness of these films are determined from the regression analysis of SE data, which are corroborated using TEM and AFM technique. Highly a-axis oriented AlN film grown at 400 C, exhibits high n and low k at 210 nm (deep-UV region) with a small birefringence and dichroism near to band edge, which can be used in isotropic deep UV optoelectronic device applications. All these AlN films exhibit transparent nature from near-infrared (NIR) to 354 nm, where optical band gap energies vary between 5.7 to 6.1 eV.