Flat GaN epitaxial layers grown on Si(111) by metalorganic vapor phase epitaxy using step-graded AlGaN intermediate layers
Authors: Cheng, Kai; Leys, M.; Degroote, S.; Daele, B.; Boeykens, S.; Derluyn, J.; Germain, M.; Tendeloo, G.; Engelen, J.; Borghs, G.
Source: Journal of Electronic Materials, Volume 35, Number 4, April 2006 , pp. 592-598(7)
Abstract:In this work, we report on the growth by metalorganic vapor phase epitaxy (MOVPE) of GaN layers on AlN/Si(111) templates with step-graded AlGaN intermediate layers. First, we will discuss the optimization of the AlN/Si(111) templates and then we will discuss the incorporation of step-graded AlGaN intermediate layers. It is found that the growth stress in GaN on high-temperature (HT) AlN/Si(111) templates is compressive, although, due to relaxation, the stress we have measured is much lower than the theoretical value. In order to prevent the stress relaxation, step-graded AlGaN layers are introduced and a crack-free GaN epitaxial layer of thickness >1 µm is demonstrated. Under optimized growth conditions, the total layer stack, exceeding 2 µm in total, is kept under compressive stress, and the radius of the convex wafer bowing is as large as 119 m. The crystalline quality of the GaN layers is examined by high-resolution x-ray diffraction (HR-XRD), and the full-width-at-half maximums (FWHMs) of the x-ray rocking curve (0002) -scan and (−1015) -scan are 790 arc sec and 730 arc sec, respectively. It is found by cross-sectional transmission electron microscopy (TEM) that the step-graded AlGaN layers terminate or bend the dislocations at the interfaces.
Document Type: Research Article
Affiliations: Email: email@example.com
Publication date: April 1, 2006