Nearly stress-free substrates for GaN homoepitaxy
2006 (English)In: Journal of Crystal Growth, ISSN 0022-0248, Vol. 293, no 2, 462-468 p.Article in journal (Refereed) Published
High-quality 300 µm thick GaN crack-free layers grown by hydride vapor phase epitaxy (HVPE) on c-plane sapphire without buffer layers and separated from the substrate by laser lift-off were investigated by high resolution X-ray diffraction (XRD), low-temperature photoluminescence and cathodoluminescence. All these characterization techniques confirm the high structural quality of the resulting material. Lateral X-ray mapping of the free-standing bulk-like GaN shows a homogeneous compressive stress of less than 40 MPa and a heterogeneous stress of about 80 MPa. The formation of twin grains (domains) were observed both in the reciprocal space mapping of the (2 0 .5) reflection and in rocking curve measurements. The latter ones revealed an estimated lateral coherence length of about 1.2 µm. The crystallite size along the c-axis is estimated to be larger than 20 µm. An upper limit of the density of dislocations with a component of the Burgers vector along the c-axis (screw and mixed type) of 1.3×107 cm-2 was extracted from the XRD data, while transmission electron microscopy measurements revealed a dislocation density of 1.7×107 cm-2. Thus, these layers are suitable as lattice-parameter and thermal-expansion matched substrates for strain-free homoepitaxy of GaN-based device heterostructures. © 2006 Elsevier B.V. All rights reserved.
Place, publisher, year, edition, pages
2006. Vol. 293, no 2, 462-468 p.
A1. Cathodoluminescence, A1. High resolution X-ray diffraction, A1. Photoluminescence, A1. Stress, A3. Hydride vapor phase epitaxy, B1. III-Nitrides
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-50161DOI: 10.1016/j.jcrysgro.2006.05.058OAI: oai:DiVA.org:liu-50161DiVA: diva2:271057