Enhancement of the energy photoconversion efficiency through crystallographic etching of a c-plane GaN thin film

Antonio M. Basilio; Yu-Kuei Hsu; Wen-Hsun Tu; Cheng-Hsuing Yen; Geng-Ming Hsu; Oliver Chyan; Yieu Chyan; Jih-Shang Hwang; Yit-Tsong Chen; Li-Chyong Chen; Kuei-Hsien Chen

doi:10.1039/C0JM00704H

Enhancement of the energy photoconversion efficiency through crystallographic etching of a c-plane GaN thin film†

Antonio M. Basilio,^ab Yu-Kuei Hsu,^c Wen-Hsun Tu,^c Cheng-Hsuing Yen,^d Geng-Ming Hsu,^e Oliver Chyan,^f Yieu Chyan,^g Jih-Shang Hwang,^d Yit-Tsong Chen,^bc Li-Chyong Chen*^e and Kuei-Hsien Chen*^ce

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* Corresponding authors

^a Taiwan International Graduate Program, Academia Sinica, 128 Academia Road, Section 2, Nangkang, Taipei, Taiwan

^b Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan

^c Institute of Atomic and Molecular Sciences, Np. 1, Roosevelt Road, Sec. 4, Taipei, Taiwan
E-mail: chenkh@pub.iams.sinica.edu.tw
Fax: +886-2-2362-0200
Tel: +886-2-2362-0212

^d Institute of Optoelectronic Science, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung, Taiwan

^e Center for Condensed Matter and Sciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan
E-mail: chenlc@ccms.ntu.edu.tw
Fax: +886-2-2365-5404
Tel: +886-2-3366-5249

^f Department of Chemistry, University of North Texas, 1155 Union Circle, #305070 Denton Tx

^g Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA

Abstract

Using a simple and inexpensive crystallographic etching technique on a GaN thin film, the energy photoconversion efficiency was increased by 100%. Prior to etching, the thin film's solar-to-hydrogen conversion efficiency at the applied bias of 0.5 V versus the counter electrode in 1.0 M HCl solution was 0.37%. After etching, the efficiency doubled to 0.75%. After five hours of continuous gas collection, the unetched GaN thin film yielded a stable photocurrent of 0.41 mA cm⁻² which produced 0.10 mL of H₂ gas. The etched sample, on the other hand, resulted in an improved stable photocurrent of 0.83 mA cm⁻² and yielded a greater volume of 0.70 mL of H₂ gas, with the presence of H₂ confirmed through gas chromatography. Further investigations have shown that the increased hydrogen generation capacity was possibly caused by three factors: one, increase in surface area caused by the etching process; two, decrease in surface donor concentration caused by the etching as probed through Mott-Schottky plots; and three, the appearance of stepped edges and etched facets that show greater photocatalytic activity than the original c-plane when probed through the photodeposition of Ag particles.

Journal of Materials Chemistry

Enhancement of the energy photoconversion efficiency through crystallographic etching of a c-plane GaN thin film†

Abstract

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