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GaN microcavities formed by laser lift-off and plasma etching

Martin, Robert and Kim, H.S. and Cho, Y. and Edwards, P.R. and Watson, I.M. and Sands, T. and Cheung, N.W. and Dawson, M.D. (2002) GaN microcavities formed by laser lift-off and plasma etching. Materials Science and Engineering B, 93 (1-3). pp. 98-101. ISSN 0921-5107

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Photoluminescence measurements are used to investigate GaN microcavities formed between two all-oxide distributed Bragg reflectors. The structures are fabricated using a combination of laser lift-off to separate MOVPE-grown epitaxial GaN layers from their sapphire substrates, inductively coupled plasma etching to thin the GaN and electron-beam evaporation to deposit silica/zirconia multilayer mirrors. The first mirror is deposited on the as-grown GaN surface before bonding to a silicon substrate for the laser lift-off process, which uses a 248 nm KrF laser to selectively decompose GaN at the GaN/sapphire interface. The second dielectric mirror is deposited on the GaN surface exposed by the substrate removal, in some cases following an etch-back stage. This etch-back, achieved using inductively coupled plasma and wet chemical etching, allows removal of the low-quality GaN nucleation layer, control of the cavity length and modification of the exposed surface. Photoluminescence measurements demonstrate cavity-filtered luminescence from both etched and non-etched microcavities. Analysis of the observed modes gives cavity finesses of approximately 10 for 2.0 and 0.8 μm GaN cavities fabricated from the same wafer, indicating that the etch-back has had little effect on microcavity quality.