Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: GaN: preparation and characterization I

HL 27.7: Talk

Wednesday, March 25, 2009, 11:15–11:30, BEY 81

Screening Dynamics of the Spontaneous Polarisation Field in GaInN/GaN Quantum Well Structures — •Martina Finke, Daniel Fuhrmann, Holger Jönen, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — TU Braunschweig, Institut für Angewandte Physik, Braunschweig

In GaN-based quantum well structures, the spontaneous and piezoelectric fields lead to the quantum confined Stark effect, which causes a decrease in the effective bandgap and a reduction of the oscillator strength and therefore the intensity of emitted light. The piezoelectric polarization was measured experimentally by various methods, but the spontaneous field as a bulk property is usually screened by charged species on the surface and was not accessible to direct experimental determination up to now. We use GaInN quantum wells as a sensitive probe for the magnitude and changes of the spontaneous field. The samples are investigated by cathodoluminescence and photoluminescence in an UHV environment. One the one hand the electron beam activates the spontaneous field by removal of charges at the surface. On the other hand, electron hole pairs generated in the bulk tend to screen the field. The complex dynamics are observed as a shift of spectral position and an intensity variation. By variation of electron beam penetration depth, cap thickness and doping level we study the different time dependent behaviour in screening and descreening of the spontaneous field.