A pulsed EDMR study of hydrogenated microcrystalline silicon at low temperatures

Abstract

Experimental results of pulsed electrically detected magnetic resonance (pulsed EDMR) measurements are reviewed with regard to the question for microscopic mechanisms that determine the lifetimes of excess charge carriers in hydrogenated microcrystalline silicon. The results show that two qualitatively different dangling bond (db) recombination processes occur. (i) Distant pair recombination through shallow conduction band tail states (CE centers) and dbs and (ii) a db direct capture (dc) recombination where charge carriers localize directly at dbs. For the db-dc process, it is shown that an intermediate, excited triplet state of the db exists which lies about 50meV below the conduction band edge. The recombination probabilities of this path are quantified by means of pulsed EDMR. The temperature and light intensity dependencies suggest that under the experimental conditions given, the db-dc process is not only electronically more active in comparison to the CE-db process, it is even the determining process for the lifetime of excess charge carriers.

Electrical detection of electron spin resonance in microcrystalline silicon pin solar cells

“…For this to occur, both centres must either be involved in the same microscopic process or two different processes involving the two paramagnetic centres separately, but influence I ph in a similar way [46]. Based on the experimental results we cannot unambiguously discriminate between both possibilities, but in any case the correlation between the pEDMR transients supports the interpretation that both signals stem from spin-dependent processes in the n-a-Si:H layer.…”

Transport and recombination through weakly coupled localized spin pairs in semiconductors during coherent spin excitation

“…However, when coherent effects are studied with pulsed techniques ͑PEDMR/PODMR͒, [13][14][15][16][17] the interpretation of the experiments relies strongly on the proper theoretical description of spin interaction during coherent microwave excitation. 8,13 An example for the difference between a PEDMR signal and an ESR signal that come from the same spin ensemble are weakly exchange and weakly dipolar coupled distant pair states in the band gap of an arbitrary semiconductor material with weak spin-orbit coupling as described analytically by Boehme and Lips. 14 Weak spin-spin coupling means that the exchange coupling constant J and dipolar coupling strength D d as defined in Ref.…”

“…Examples for such systems could be donor-acceptor pairs whose distance is sufficiently large, yet not large enough to make donor-acceptor recombination impossible, 18 donor deep defect recombination at crystalline silicon surfaces, or equivalently, trap-dangling bond recombination in disordered silicon materials such as amorphous or microcrystalline silicon. 8,19 Weak spin-orbit coupling is required in order to ensure spin conservation and, therefore, a spin-selection rule. It is fulfilled, for instance, in all known silicon morphologies but also in many organic semiconductor materials.…”

Coherent defect spectroscopy with pulsed optically and electrically detected magnetic resonance

“…Figure 1 states. Beside D-A recombination [15], spin-dependent recombination has been observed in a variety of qualitatively different mechanisms such as weakly bound excitonic states and tail-tail recombination [7,16] (the experimental data reviewed in sections 4 and 5 will be concerned with these examples), bandtail-deep defect recombination [17] or direct capture recombination at deep defects [18]. Even though all these mechanisms are of quite different microscopic nature, they can all be spin dependent as long they involve electronic transitions between two paramagnetic states.…”