Deposition of Boron Doped Zinc Oxide Films and Their Electrical and Optical Properties

Abstract

Boron doped zinc oxide films were deposited by atmospheric pressure chemical vapor deposition in a laminar flow reactor from diethyl zinc, tert‐butanol, and diborane in the temperature range from 300 to 420°C. When the deposition temperature was above 320°C, both doped and undoped films have highly oriented crystallites with their c‐axes perpendicular to the substrate plane. Films deposited from 0.07% diethyl zinc and 2.4% tert‐butanol have electron densities from 3.5 to , conductivities from 250 to 2500 Ω−1 cm−1, and mobilities from 2.5 to 35.0 cm2/V‐s, depending on dopant concentration, film thickness, and deposition temperature. Optical measurements show that the maximum infrared reflectance of the doped films is close to 90%, compared to about 20% for undoped films. Visible absorption and conductivity were found to increase with thickness. The ratio of conductivity to visible absorption coefficient for doped films was from 0.1 to 1.1 Ω−1. The bandgap of the film changes from 3.3 to 3.7 eV when the film is doped with 0.012% diborane.