Optical and Spectroscopic Ellipsometric Study of Indium Boron Nitride Sputtered Thin Films with Low Boron Concentration
- PDF / 1,129,618 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 42 Downloads / 222 Views
Optical and Spectroscopic Ellipsometric Study of Indium Boron Nitride Sputtered Thin Films with Low Boron Concentration Mohammad A. Ebdah1, Martin E. Kordesch1, David C. Ingram1, Hamad AlBrithen2, AbdelRahman A. Ibdah3, and Kevin Cooper1. 1 Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA. 2 Physics and Astronomy Department, King Abdullah Institute for Nanotecnology, King Saud xUniversity, Riyadh, Saudi Arabia. 3 Department of Physics and Astronomy, the University of Toledo, Toledo, OH 43606, USA. ABSTRACT Amorphous indium boron nitride (a-InBN) thin films were successfully fabricated using radio frequency (RF) magnetron sputtering, and were deposited onto fused silica and c-Si(100) substrates. Sputtering was achieved using a target of polycrystalline B and In species with B/In nominal at.% ratio of 25/75 under the flow of nitrogen. The structure and composition of the films have been investigated by X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The XRD patterns reveal that the sputtered films are amorphous, and the XPS confirms the presence of boron in the films in addition to an oxide overlayer. The optical absorption of samples grown on silica was obtained using spectrophotometry (SP) technique in the wavelength range (200 - 800) nm. Analysis of the absorption coefficients using the Tauc linear extrapolation gives an optical bandgap of 2.05 eV, indicating a higher bandgap comparing to the measured optical bandgap of a-InN (1.25 eV) due to doping with boron. Films grown on cSi(100) were characterized by spectroscopic ellipsometry (SE) technique in the wavelength range of (300-1700) nm. The measured ellipsometric spectra are described well by a two-layer model structure, which consists of a transparent layer on top of an absorbing layer. The thicknesses and optical functions of the transparent and absorbing layers were obtained by analyzing the measured ellipsometric spectra, Ψ and Δ within the framework of the Cauchy– Urbach (CU) and Tauc–Lorentz (TL) models, respectively. While the overlayer is completely transparent over the measured range (k(λ) = 0), the absorbing layer underneath it exhibits a clear absorption above its optical bandgap of 2.15 eV, which is in a good agreement with the SP finding. There was an excellent agreement between the bandgap obtained as a fitting parameter from the optical model and that obtained by linear extrapolation using the empirical Tauc and Cody models for amorphous semiconductors. INTRODUCTION Nitride semiconductors have been recently of great consideration in optical coating and optoelectronic applications [1, 2]. The ability to vary the bandgap in ternary semiconductors of the form AxB1-xN over a wide range of the composition at. %, x, is one reason for the interest in fabricating and designing such materials [3], where the engineered bandgap is related directly to many application such as light emitting diodes (LED), and laser applications. However, certain properties of the end binary members AN and BN could in
Data Loading...
