SKM 2021 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 19: Poster Session IV

HL 19.19: Poster

Donnerstag, 30. September 2021, 13:30–16:30, P

Pump-probe measurements to detect ultra-fast carrier dynamics and carrier density saturation in GaN-based quantum wells — •Malte Schrader, Philipp Henning, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institut für Angewandte Physik & Laboratory for Emerging Nanometrology, Technische Universität Braunschweig, 38106 Braunschweig, Germany

The aim of our study is to understand the carrier dynamics in GaN-based quantum wells at high carrier densities. An accurate estimation of the excited charge carrier density in pulsed laser experiments by indirect fluence-to-charge-density conversion is flawed, because the available states for the excited electrons in the conduction band might already be completely filled by the high fluence laser pulse.

We therefore show in this contribution a direct approach by using two pulsed laser beams in quick succession in a pump-probe setup: a pump beam excites the carriers and a probe beam measures the transmission shortly thereafter, and therefore the occupation of the states above the band edge. A laser pulse duration of 35 fs at 5 kHz repetition rate is used in a degenerate setup, meaning pump and probe beam have the same wavelength. The decay of the excited carrier states is encoded in the transmitted probe beam as a function of the delay between pump and probe beam. To detect a saturation limit the fluence of the pump beam is increased. Besides two distinct decay times of around 10 ps and several 100 ps respectively, the ultra-fast intraband relaxation in the fs domain is of special interest.