AlGaN epitaxial layers grown by HVPE on sapphire substrates

Abstract

AbstractGrowth of AlxGa1–xN (x ∼ 0.0‐1.0) alloy layers by hydride vapor pahse epitaxy (HVPE) is reported. Crack‐free undoped AlGaN layers from 0.1 to 2 μm thick were grown on 2″ SiC and 2″and 4″ sapphire substrates. For AlxGa1–xN (x ∼ 0.7‐0.8) layers grown on sapphire, high‐resolution symmetric/asymmetric X‐ray diffraction (XRD) measurements resulted in ω‐scan rocking curve widths ranging from 250 to 650 arcsec and from 1400 to 1900 arcsec, for the (00.2) and (10.2) reflections, respectively. Minimum XRD‐estimated screw and edge dislocation densities in AlGaN layers grown on sapphire were <6 x 108 cm–2 and <2 x 109 cm–2, respectively. Raman studies revealed that the composition dependences of the phonon modes of HVPE‐grown AlxGa1–xN layers are in a good agreement with the one, which have been observed for MOCVD‐grown AlxGa1–xN alloys earlier. Grown layers had n‐type electrical conductivity for the composition range up to x = 0.4. The layer became highly resistive for higher AlN contents. First results on 40 µm thick crack free AlGaN growth on SiC substrates are reported. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)