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Patterning of sapphire substrates via a solid state conversion process

Published online by Cambridge University Press:  01 February 2005

Hyoungjoon Park ,
Helen M. Chan  and
Richard P. Vinci
Hyoungjoon Park
Affiliation:
Center for Optical Technologies and Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015
Helen M. Chan
Affiliation:
Center for Optical Technologies and Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015
Richard P. Vinci
Affiliation:
Center for Optical Technologies and Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015
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Abstract

Nanopatterned sapphire substrates offer the potential for improved performance of devices based on III-V nitrides, e.g., light-emitting diodes and laser diodes. Due to the chemical stability and hardness of sapphire, however, surface patterning is a time-consuming and expensive process. Therefore, a novel method was utilized, whereby a surface coating of Al was deposited on a sapphire substrate and patterned into an array of square mesas using e-beam lithography. The lateral dimensions of each mesa were approximately 400 × 400 nm, and the average height was approximately 100 nm. The metallic film was subsequently subjected to an oxidation treatment at 450 °C for 24 h (a heat treatment which had previously been shown to minimize hillock formation). For the second heat treatment, which is necessary to induce migration of the sapphire interface and hence achieve solid state conversion, a range of temperatures (800–1350 °C) was explored. Results showed that for a heat-treatment time of 1 h, pattern retention was achieved for annealing temperatures less than or equal to 1250 °C. Successful epitaxial conversion of the patterned mesas to sapphire was confirmed using electron backscatter diffraction.

Keywords

Crystal growthEpitaxyThin film
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 2 , February 2005 , pp. 417 - 423
Copyright
Copyright © Materials Research Society 2005

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