Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 16: III-V semiconductors II
HL 16.8: Vortrag
Dienstag, 24. März 2009, 11:30–11:45, POT 151
Pulsed Growth of AlN by MOVPE — •Hanno Kröncke, Stephan Figge, and Detlef Hommel — Institute for Solid State Physics (IFP), University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen
The growth of AlN is of interest because of it’s special features like high thermal conductivity and large bandgap. These provide applications like high power- or opto-electronic devices in the UV. However the production of high quality AlN templates is challenging because of the low diffusivity of Al, which inhibits lateral overgrowth and demands high growth temperatures over 1300 ∘C to decrease the defect density. A second approach is the pulsed or flow modulation MOVPE growth [1], where an alternating supply of the precursors TMA and NH3 increases the surface mobility of the atoms. This allows for growing AlN even at temperatures of 800 ∘C [2].
In our study we grew thick AlN layers on c-plane sapphire in a closed coupled showerhead MOVPE at temperatures of 1000 ∘C. We investigated the influence of nitridation, different seed layers and length of precursor pulses on the surface roughness, cracking and crystal quality by AFM, SEM and XRD. Especially a nitridation and low temperature AlN buffer lead to a rough surface, so that we developed a process starting with pure TMA supply. By this method we achieved more than 1 µm thick AlN layers with an RMS roughness below 1 nm, which show no cracks and high crystal quality.
[1] M. Asif Kahn, Appl. Phys Lett. 61 (1992), 2539
[2] Jung-Seung Yang, Jap. J. App. Phys. 46, 38, (2007), L927