Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 38: ZnO and Related Semiconductors

HL 38.12: Talk

Wednesday, March 24, 2010, 12:30–12:45, H17

A novel method to determine optical emission rates of defect-trapped electrons with high precision — •Martin Ellguth, Florian Schmidt, Matthias Schmidt, Holger v. Wenckstern, Rainer Pickenhain, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II

The properties of defects as the primary factor influencing the electrical behaviour of a semiconductor are one of the most important targets of semiconductor research, especially in novel materials like ZnO where the causes of unintended electrical behaviour in fabricated samples are often unknown. Existing publications on defects in ZnO report the activation energy and the carrier capture cross-section as well as occurence of defects in specially prepared samples. We extend this data set by providing photo cross-section spectra with the high accuracy necessary to determine meaningful values for the Franck-Condon parameter. A novel technique to reliably determine the emission rates of defect-trapped electrons excited by photon absorption ("optical" emission) is presented. It is similar to isothermal DLTS. Long transients (up to 1 hour) are digitally recorded while the sample is illuminated with monochromatic light and transformed into a rate spectrum. Varying the photon energy, the rates of optical emission processes can be determined from each spectrum to enable the calculation of the photo cross-section spectra with excellent precision. The thermal binding energy of a very deep defect not accessible in standard DLTS has been estimated from such a spectrum by applying a model from [1].

[1] A. Chantre, G. Vincent, D. Bois, Phys. Rev.~B 23, 5335 (1981)