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HL: Halbleiterphysik

HL 2: Störstellen I

HL 2.6: Talk

Monday, March 17, 1997, 11:45–12:00, H1

Long-living Shallow Donor Excited States of GaP:Te — •S. D. Ganichev^1,2, I. N. Yassievich², W. Raab¹, E. Zepezauer¹, and W. Prettl¹ — ¹Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg — ²A. F. Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021, Russia

Long-living shallow donor excited states in semiconductors existing forseveral miliseconds have been observed. Te-donors in GaP have been ionized by means of phonon assisted tunneling in the electric field of pulsed far-infrared laser radiation. The measurements have been carried out in the temperature range of 20-90 K using radiation of wavelength between 35 and 280 µm and intensities up to 1 MW/cm². The photocunductive signal caused by ionization in response to the laser pulse shows in addition to a fast component (of the order 100 ns) a second component rising after the exciting pulse has ceased and afterwards decaying exponentially. This decay has a strongly temperature dependent time constant varying from microseconds to several miliseconds. It is shown that this complex temporal structure of the signal is caused by a storage of carriers in the valley-orbit split 1s(E) Te shallow donor state. Furthermore it has been proved by the observation of far-infrared to mid-infrared up-conversion that the final step of recombination is achieved by radiative transitions.