Geminate Recombination Model Research Articles

Novel coulomb glass creation in electronic one dimensional systems

Experimental evidence is presented that demonstrates how a light pulse incident upon a 1D semiconductor, PDATS, in zero field, seeds that semiconductor with charge held in a stable state, unrecombined, for times on the order of milliseconds. Application of an electric field at later time releases some of this seed charge which is measured whilst the remainder recombines. The fraction that is released is dependent on electric field in a fashion describable in terms of the Onsager model of geminate recombination in 1D. Two models for this effect are put forward and discussed. In the first a distribution of traps are available to hold the carriers for long times. The second model involves the formation of interchain excitons and coulomb glass states to hold the charge.

Pulsed radiation-induced attenuation in certain optical fibers

Using the X-ray pulse from the HERMES II simulation machine at Sandia National Laboratories, the author measured the pulsed radiation-induced attenuation in two optical fibers considered to be 'non-rad-hard': the 50 mu m core graded-index fiber from Corning and the plastic (PMMA) fiber from the Mitsubishi Rayon Company. These fibers were exposed to radiation up to doses of 19.5 and 28 krad(Si), respectively. In addition, fits of their postradiation recovery were made to the geminate recombination model, from which the recombination rate and generation constants, characteristic of this theory, were determined. These parameters should be useful in determining the response of the fibers to radiation conditions other than those encountered here. >

Charge carrier photogeneration on some substituted polyacetylenes

The photogeneration of charge carriers was studied with the following polymers: poly-[N-(2-propinyl)-phenothiazine] (PPPT) and copolymers of N-(2-propinyl)-carbazole with N-(2-propinyl)-phenothiazine (PCz+PPT) and N-(2-propinyl)-carbazole with phenylacetylene (PCz+PA). In the case of PCz+PA, the experimentally found dependence of the photogeneration efficiency on the strength of an externally applied electric field could be well fitted with the curve calculated on the basis of Onsager's model of geminate recombination. In the cases of PPPT and PCz+PPT, on the other hand, the experimental values deviated strongly from the theoretical curve at field strengths between 106 and 107 V/m.

Carrier photogeneration and mobility in polydiacetylene: Fast transient photoconductivity.

Transient photoconductivity experiments have been carried out on single crystals of polydiacetylene-(bis p-toluene sulfonate), PDA-TS. The low--electric-field photocurrent decay consists of a temperature-independent fast (picosecond) initial component and a longer-time (nanosecond) component with magnitude that is strongly temperature dependent. Using very small spacings between electrodes on the sample, we have succeeded in achieving sweepout for the longer-lived carriers; the data yield a mobility of \ensuremath{\approxeq}5 ${\mathrm{cm}}^{2}$/V\ensuremath{\cdot}s at room temperature in the nanosecond regime. These results demonstrate that the Onsager geminate recombination model, previously used extensively for the polydiacetylenes, is not applicable to PDA-TS.

Photoresponse of polyacetylene junctions: A geminate recombination model

A theoretical model is presented for the photocurrent spectral response of Schottky junctions on semiconducting polyacetylene, taking into account geminate recombination of electron-hole pairs and pair dissociation. Comparison with available experimental data is made, showing fair agreement.

Geminate recombination-controlled photogeneration in amorphous solids

Experimental and theoretical results are presented which suggest a unified picture of photogeneration processes in amorphous selenium and hydrogenated amorphous silicon. The different wavelength dependent quantum efficiency of photogeneration in these technologically important materials can be explained by a geminate recombination model if account is taken of their different dielectric constants.

Spin dependent recombination and luminescence in amorphous silicon

The non resonant and resonant luminescence change observed in amorphous glow discharge silicon is analyzed using a simple Donor-Acceptor type recombination model. It is proposed that quenching lines are related to anomalously spin dependent non radiative transitions which are in competition with normally spin dependent radiative ones. A signal sign change is predicted to occur with increasing chopping frequency of the microwave power and this is related to experiment. Though similar effects can be obtained using a model of geminate recombination with singlet spin memory, it is argued that for the resonant change this possibility can be dismissed on the grounds of exchange coupling.