Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 7: III-V semiconductors I

HL 7.1: Vortrag

Montag, 26. März 2007, 11:00–11:15, H17

Strain properties of AlN layers grown on different substrates — •Ronny Kirste¹, Ute Haboeck¹, Axel Hoffmann¹, Christian Thomsen¹, Barbara Bastek², Frank Bertram², Jürgen Christen², Armin Dadgar², and Alois Krost² — ¹Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany — ²Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany

We present results of micro-Raman investigations on AlN samples grown by MOCVD on silicon and sapphire substrates. Thermal and lattice mismatch lead to a strong tensile strain in case of growth on silicon. Thus, already thin layers tend to relax by cracking. In the vicinity of such cracks we observed a strong shift of the nonpolar E₂(high) line. This mode is suitable to probe the strain properties because it is not affected by free carriers or internal electric fields. Converting this shift we found strain gradients of about 1 GPa in 300 nm thick layers and less than 0.5 GPa in thicker films of 1 or 2 µm. Even, at the center of the cracks the AlN layers are not fully relaxed. We will discuss the reasons, therefore, in comparison to AlN samples grown on sapphire. AlN on sapphire is, contrarily to growth on silicon, almost relaxed or slightly and uniformly compressive strained. Apart from cracking good crystal quality is achieved in both cases.