Regensburg 2007 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Fachverband Halbleiterphysik
HL 42: GaN: devices
HL 42.9: Vortrag
Donnerstag, 29. März 2007, 16:00–16:15, H13
All-optical determination of the lateral electric field in InGaN/GaN quantum wells — •Clemens Vierheilig1, Ulrich T. Schwarz1, Werner Wegscheider1, Nikolaus Gmeinwieser2, Uwe Strauß2, and Volker Härle2 — 1NWF II - Physik, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg — 2Osram Opto Semiconductors, Wernerwerkstraße 2, 93049 Regensburg
Photogenerated carriers in InGaN/GaN quantum wells are vertically separated by strong internal piezoelectric fields. When exciting the sample with a small laser spot, the initial carrier density follows the excitation profile. Due to the carrier density-dependent screening of the piezoelectric field, a strong lateral dependence of the quasi Fermi-levels for electrons and for holes is induced by the reduction of the quantum confined Stark effect (QCSE). This gradient in the quasi Fermi-levels defines a lateral electric field with different directions for electrons and holes, so that both types of carriers are pushed laterally away from the excitation spot. An additional lateral diffusive motion is induced due to the concentration gradient. From the spatial distribution of the PL-signal of a green emitting InGaN/GaN quantum well test layer, measured by a modified confocal microscope, we calculate a radial electric field with a maximum value of about 110 V/cm.