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HL: Fachverband Halbleiterphysik

HL 80: GaN: Preparation and Characterization V (mainly Cathodoluminescence)

HL 80.5: Vortrag

Donnerstag, 29. März 2012, 12:15–12:30, ER 270

Spontaneous polarization of GaN derived from stacking fault luminescence — •Jonas Lähnemann¹, Oliver Brandt¹, Uwe Jahn¹, Carsten Pfüller¹, Claudia Roder¹, Pinar Dogan¹, Frank Grosse¹, Abderrezak Belabbes², Friedhelm Bechstedt², Achim Trampert¹, and Lutz Geelhaar¹ — ¹Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin — ²Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Wurtzite crystals exhibit a spontaneous polarization P_sp in equilibrium, which together with the piezoelectic polarization leads to electric fields in heterostructures and thus has an immediate impact on device design. Amongst these, GaN stands out as the material used for solid-state lighting. So far, only an indirect experimental determination of P_sp for GaN has been reported using a thermodynamic approach and theoretical predictions exhibit a significant variation.

We derive P_sp for GaN from the emission energies of excitons bound to different types of stacking faults (SFs). Employing micro-photoluminescence and cathodoluminescence spectroscopy, we observe emission lines from the intrinsic and extrinsic SFs in strain-free GaN micro-crystals. By treating the sheet charges associated with these SFs as a plate capacitor, we obtain P_sp from the observed transition energies. To support our model, we use self-consistent Poisson-Schrödinger calculations and density functional theory. This approach should be applicable also to other wurtzite semiconductors.