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HL: Halbleiterphysik

HL 26: II-VI semiconductors II

HL 26.3: Vortrag

Dienstag, 28. März 2006, 15:45–16:00, POT 51

Alloy Fluctuations and Phase separation in ZnCdO Layers: Thermalization and Carrier Freeze Out — •Alexander Franke¹, Thomas Hempel¹, Silke Petzold¹, Frank Bertram¹, Jürgen Christen¹, R. Kling², Christoph Kirchner², and Andreas Waag³ — ¹Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany — ²Department of Semiconductor Physics, Ulm University, Germany — ³Department of Semiconductor Technology, Braunschweig Technical University, Germany

An inherent problem for the epitaxial growth ZnCdO is a different crystallization of ZnO and CdO into wurtzite and rock-salt structure, respectively resulting in local stoichiometry fluctuation and decomposition up to phase separation. A series of MOCVD grown Zn_1−xCd_xO layers with systematically increasing Cd-content (0.3%–2.0%) were analyzed using photoluminescence spectroscopy (PL). A systematic red-shift (3.239eV–3.150eV) and broadening of the PL peak is observed with increasing [Cd] merging into a splitting into two well distinguished peaks. While the high energetic main PL peak (dominant Cd-concentration) shows a linear excitation density dependence over more than 4 orders of magnitude, a super-linear dependence is found for the evolving satellite peak (minor Cd-rich local phase). The temperature dependence exhibits a pronounced s-shape behavior of the peak energy characteristic for thermalization and freeze out of the carriers in local potential fluctuations. The PL results are compared with highly spatially resolved cathodoluminescence directly visualizing the Cd-fluctuations and the phase separation.