Photoluminescence in high-quality a-Ge : H

We present quadrature frequency resolved spectroscopy (QFRS) measurements o f photoluminescence (PL) in photoconductive and luminescent films of a-Ge:H with a defect density approximate to 1 x 10(16) cm(-3) obtained from elect ron cyclotron resonance (ECR) plasma chemical vapor deposition (PCVD), toge ther with a study of PL and PL excitation (PLE) spectra. A double-peak life time distribution is observed with a short lifetime at approximate to 1 mu s and a long one at approximate to 0.1 ms as observed in a-Si:H. The depend ence of the two lifetimes and their corresponding relative quantum efficien cies on the e-h pair generation rate and temperature is also investigated. The occurrence of double peaks is attributed to the radiative recombination from singlet and triplet exciton states, and the exchange energy between s inglet and triplet states is estimated to be approximate to 3.3 meV in a-Ge :H. (C) 2000 Published by Elsevier Science B.V. All rights reserved.