• Renard, J.
• Ruterana, Pierre
• Gayral, B.
• Chauvat, Marie-Pierre
• Lahourcade, L.
• Monroy, Eva

Abstract

International audience ; GaN directly deposited on m-sapphire by plasma-assisted molecular-beam epitaxy settles into two main crystalline orientation domains: GaN﴾112¯2﴿ and GaN{101¯3}. The dominant phase is GaN﴾112¯2﴿ with <112¯3¯>GaN║ <0001>sapphire and <11¯00>GaN║ <112¯0>sapphire in-plane epitaxial relationships. Deposition of GaN on top of an AlN﴾112¯2﴿ buffer layer and growth under slightly Ga-rich conditions reduce GaN{101¯3} precipitates below the detection limits. Studies of Ga adsorption demonstrate that it is possible to stabilize up to one Ga monolayer on the GaN﴾112¯2﴿ surface. The presence of this monolayer of Ga excess on the growth front reduces the ﴾112¯2﴿ surface energy and hence minimizes the surface roughness. Photoluminescence from two-dimensional GaN﴾112¯2﴿ layers is dominated by a near-band-edge emission, which is assigned to excitons bound to stacking faults, present with a density around 3x105 cm−1.

Topics

• Deposition
• density
• impedance spectroscopy
• surface
• photoluminescence
• phase
• mass spectrometry
• precipitate
• two-dimensional
• surface energy
• stacking fault