Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 31: III-V-Compounds: Nitrides
HL 31.9: Talk
Tuesday, March 15, 2011, 12:30–12:45, POT 51
Growth of AlN on c-plane sapphire by pulsed MOVPE — •Hanno Kröncke, Stephan Figge, and Detlef Hommel — Institut für Festkörperphysik, Universität Bremen
Due to it’s large bandgap and it’s high thermal conductivity Aluminumnitride is of high interest for applications in high power electronics and optoelectronic device emitting in the ultra-violet region. Because Al shows a low surface diffusivity AlN is normally grown at high temperatures up to 1300 ∘C. An alternative approach is the pulsed or flow modulation MOVPE growth, where an alternating supply of the precursors increases the surface mobility of the atoms.
In this study Al-polar AlN layers with a thickness between 200 nm and 1 µm were directly grown on c-plane sapphire in a closed coupled showerhead MOVPE at temperatures between 1000 and 1250 ∘C. Beside the variation of the pulse length for precursors, different types of pre-growth treatments have been investigated. The crystal quality, expressed by surface morphology and dislocation density, was mainly characterized by HRXRD, SEM, AFM and also compared to continuously grown samples.
In general the crystal quality is very sensitive to the growth-start and common concepts, known from the growth of GaN, like low temperature nitridation and buffer layers, lead to very rough surface and high mosaicity. With optimized parameter we achieved RMS surface roughness is below 1 nm and dislocation densities, determined by XRD, in the order of 1· 107 cm−2 (screw type) and 3· 1010 cm−2 (edge type).