Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 34: Poster I: III-V Semiconductors

HL 34.37: Poster

Tuesday, March 23, 2010, 18:30–20:30, Poster D2

Behaviour of the spontaneous polarisation field in polar and nonpolar GaInN/GaN quantum well structures — •Martina Finke, Holger Jönen, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institut für Angewandte Physik, TU Braunschweig, Germany

The spontaneous and piezoelectric fields in wurtzite GaN-based quantum well structures induce the quantum confined Stark effect(QCSE). The QCSE causes a decrease in the effective bandgap and a reduction of the oscillator strength in the polar c-direction. Unlike in case of the polar direction, the electric fields and the QCSE vanishes in the nonpolar directions, like m-plane. We use GaInN quantum wells as a sensitive probe for the magnitude and changes of the spontaneous field. By using cathodoluminescence in an UHV environment we were able to investigate field induced effects in the polar direction and the absence of these effects in a nonpolar direction. The complex dynamics are observed as a shift of spectral position and a intensity variation. Various samples grown on polar and nonpolar substrates were investigated. By variation of the sample structure like cap thickness and doping level we study the different time dependent behaviour in screening and descreening of the spontaneous field at different electron beam penetration depth. In this contribution we present measurements on nonpolar heterostructures which clearly shows no electric field induced effects, like emission energy and intensity shifts. Compared to the strong effects on polar samples, these measurements prove the absence of the spontaneous field in nonpolar directions.