Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Halbleiterphysik
HL 24: GaN: Pr
äparation und Charakterisierung I
HL 24.10: Vortrag
Dienstag, 25. März 2003, 17:30–17:45, BEY/118
MOCVD growth of thick, crack free GaN on Si(111) using a graded AlxGa1−xN high temperature buffer layer — •Andreas Able und Werner Wegscheider — Institut für Angewandte und Experimentelle Physik, Universität Regensburg, 93040 Regensburg
Recently, the attention on Si(111) as a potential substrate for nitride heterostructures has grown, because of its low price, high quality and availability in a wide range of doping levels. Furthermore, there is the possibility to combine conventional Si based structures with group III-nitride films on a single wafer.
Compared to sapphire or SiC, silicon is much less suitable for growth of high quality nitride films. Large lattice mismatch (17%), large tensile mismatch in thermal expansion coefficients and film-substrate-reactions require complex buffer structures and intermediate layers.
Marchand et.al. have shown that by introducing graded AlxGa1−xN buffers, compressive stress can be induced in the films during growth, which leads to a strong reduction in total stress after cooldown1.
We have improved this concept and have grown GaN films on Si(111) with thicknesses above 2µm without cracking. The films were grown using a two step buffer system starting with a 80 - 100nm thick high temperature (1160∘C) AlN buffer, followed by a thick ( 500nm) graded AlxGa1-xN intermediate layer. Subsequently grown GaN films are crack free and of high crystal quality as shown by HRXRD. Despite the low doping efficiency in pure AlN, Si doped buffers show very low series resistance.
1JAP,89,7846(2001)