Fabrication of epitaxial III-nitride cantilevers on silicon (111) substrates

• Published in: Journal of materials science. Materials in electronics Vol. 15; no. 11; pp. 705 - 710
• Main Authors: DAVIES, S, HUANG, T. S, MURRAY, R. T, GASS, M. H, PAPWORTH, A. J, JOYCE, T. B, CHALKER, P. R
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Norwell, MA Springer 01.11.2004; Springer Nature B.V
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Mineralogy; Molecular, atomic, ion, and chemical beam epitaxy; Physics; Buffer layer; Epitaxial layers; Semiconductor materials; Gallium nitrides; Cantilever beam; Columnar structure; Film growth; Interface structure; Inductively coupled plasma; Electronic structure; Plasma etching; Aluminium nitrides; Molecular beam epitaxy; Free-standing film
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1023/B:JMSE.0000043416.67986.10

The molecular beam epitaxy of AlGaN/GaN epilayers on silicon (1 1 1) using an aluminum nitride buffer layer, and subsequent fabrication of free standing III-nitride cantilevers on Si(1 1 1) has been investigated. Transmission electron microscopy (TEM) of cross-section samples reveals a columnar structure consisting of the hexagonal gallium nitride polytype. Selected area diffraction indicates an epitaxial relationship between the gallium nitride and silicon substrate which is described by GaN[0 0 0 1]//Si[1 1 1] and GaN(1 1 0 0)//Si(1 1 1). Imaging of the electronic structure of an AlGaN/GaN interface has been investigated by mapping the variation in the plasmon frequency using an electron energy loss spectrometer on a dedicated scanning transmission electron microscope. Cantilevers were fabricated using a combination of etching processes. Nitride etch rates during inductively coupled plasma dry etch processing using a Cl^sub 2^/Ar plasma etchant were obtained by monitoring the optical reflectivity of the nitride films in situ. A peak GaN etch rate of 250 nm/min was measured, the etch rate was found to be strongly dependent on the d.c. self-bias. Thin beams of GaN having a length of 7 μm and 0.7 μm thickness, were fabricated and mechanically released from Si(1 1 1) substrates using a combination of two dry ICP etch processes, using Cl^sub 2^/Ar and CF^sub 4^/Ar/O^sub 2^ chemistries, and a potassium hydroxide (KOH) aqueous wet etch.[PUBLICATION ABSTRACT]