Rapid thermal annealing of sputter-deposited ZnO:Al films for microcrystalline Si thin-film solar cells

¹ Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, 338-8570 Saitama, Japan
² Saitama Industrial Technology Centre (SAITEC) 3-12-28 Kami-Aoki, Kawaguchi, 333-0844 Saitama, Japan
³ Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, 350-8585 Saitama, Japan

^a e-mail: shirai@fms.saitama-u.ac.jp

Received: 14 July 2011
Accepted: 2 March 2012
Published online: 26 June 2012

Abstract

Rapid thermal annealing of sputter-deposited ZnO and Al-doped ZnO (AZO) films with and without an amorphous silicon (a-Si) capping layer was investigated using a radio-frequency (rf) argon thermal plasma jet of argon at atmospheric pressure. The resistivity of bare ZnO films on glass decreased from 10⁸ to 10⁴–10⁵ Ω cm at maximum surface temperatures T_maxs above 650 °C, whereas the resistivity increased from 10^-4 to 10^-3–10^-2Ω cm for bare AZO films. On the other hand, the resistivity of AZO films with a 30-nm-thick a-Si capping layer remained below 10^-4Ω cm, even after TPJ annealing at a T_max of 825 °C. The film crystallization of both AZO and a-Si layers was promoted without the formation of an intermixing layer. Additionally, the crystallization of phosphorous- and boron-doped a-Si layers at the sample surface was promoted, compared to that of intrinsic a-Si under the identical plasma annealing conditions. The TPJ annealing of n⁺-a-Si/textured AZO was applied for single junction n-i-p microcrystalline Si thin-film solar cells.