Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 4: Ultrakurzzeitph
änomene

HL 4.4: Vortrag

Montag, 8. März 2004, 11:00–11:15, H13

THz emission from GaSb samples with modified surfaces — •Stephan Winnerl, Thomas Dekorsy und Manfred Helm — Institut für Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden

The optimization of emitters for THz radiation pulses has gained a lot of interest in recent years. They can be based on accelerating charge carriers, which are photoexcited by fs-laser pulses in the surface field of a semiconductor. We studied the THz emission from GaSb samples that were annealed at different temperatures in the range from 300 ^∘C to 700 ^∘C. Without annealing, no THz emission was observed under fs excitation at 800 nm. This is consistent with the fact, that for GaSb no surface states in the band gap have been found [1]. The THz emission was strongest for the annealing temperature of 450 ^∘C with amplitudes comparable to that of an InGaAs emitter. We attribute the THz emission to a surface field caused by decomposition of the surface of the annealed samples. The decomposition is confirmed by measuring the surface stoichiometry using Auger electron spectroscopy. We suggest that the decrease of THz intensity for the higher annealing temperatures is due to a lowering of the carrier mobility. Our experiment demonstrates the possibility to modify materials for THz emission in a very simple way.

[1] P.W. Chey, I.A. Babalado, T. Sukegawa, and W.E. Spicer, Phys. Rev. Lett. 35, 1602 (1975).