Direct measurement of the deep defect density in thin amorphous silicon films with the ‘‘absolute’’ constant photocurrent method

ABSTRACTUsing the modulated photocurrent method we studied the deep defect creation and annealing kinetics of amorphous silicon-germanium alloys with Ge fractions below 10at.%. The modulated photocurrent spectroscopy clearly discloses the existence of two distinct bands of majority carrier traps in these alloys. The bands were identified as neutral Si dangling bonds and neutral Ge dangling bonds. Our studies show clearly that the Si and Ge defects directly compete with each other during annealing, implying a global reconfiguration mechanism. The creation kinetics reveal the usual t1/3 illumination time dependence for the total deep defect density. However, the individual densities of Si and Ge defects have different time dependencies. The details of the creation and annealing kinetics of Ge and Si defects are used to test predictions of certain defect creation models.

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Hydrogenated amorphous silicon films with low defect density prepared by argon dilution: application to solar cells

Thin Solid Films ◽

10.1016/s0040-6090(01)01660-1 ◽

2002 ◽

Vol 403-404 ◽

pp. 275-279 ◽

Cited By ~ 11

Author(s):

P.P Ray ◽

P Chaudhuri ◽

P Chatterjee

Keyword(s):

Solar Cells ◽

Amorphous Silicon ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Silicon Films ◽

Argon Dilution ◽

Hydrogenated Amorphous

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On the Compensation Mechanism of Amorphous Silicon Films: Study of Stability

MRS Proceedings ◽

10.1557/proc-467-91 ◽

1997 ◽

Vol 467 ◽

Cited By ~ 3

Author(s):

D. Caputo ◽

G. De Cesare ◽

F. Palma ◽

M. Tucci ◽

C. Minarini ◽

...

Keyword(s):

Amorphous Silicon ◽

Gas Phase ◽

Formation Mechanism ◽

Boron Concentration ◽

Defect Density ◽

Silicon Films ◽

Compensation Mechanism ◽

Relevant Result ◽

Wide Range

ABSTRACTWe investigated a-Si:H compensated materials deposited over a wide range of gas dopant concentrations, from 0.125 ppm up to 103 ppm.We achieved compensation for different ratio in the gas phase of diborane and phosphine, depending on their concentration. As a relevant result, we found that at constant boron concentration compensation occurs by using two different values of phosphine flow. This behavior can be described by a change of formation mechanism involving active dopants, defects and boron-phosphorus complex, that occurs in a different way depending on the dopant concentrations.The two compensation regimes are evidenced also by a different behavior under light soaking. Furthermore we found that photocurrent evolution under illumination is determined by two concurrent mechanisms: activation of dopant species and increase of defect density.

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Recombination Process in the As-Deposited State of Hydrogenated Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-297-455 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 1

Author(s):

Jong-Hwan Yoon

Keyword(s):

Amorphous Silicon ◽

Defect Density ◽

Energy Levels ◽

Hydrogenated Amorphous Silicon ◽

Recombination Process ◽

Defect States ◽

Deep Defect ◽

Recombination Centers ◽

Hydrogenated Amorphous ◽

Deposition Conditions

Intrinsic deep defect-related recombination process has been studied in a series of undoped hydrogenated amorphous silicon(a-Si:H) films grown under different deposition conditions. Steady-state photoconductivity (σph) was measured as a function of deep defect density Nd, Urbach energy Eu, and dark Fermi energy Ef. It was found that σph strongly depends on these parameters while Ef- stays at the energy levels lower than 0.82 eV below Ec, but it is nearly independent of those while Ef stays at above 0.82 eV. These behaviors were found to be independent of the sample deposition conditions. These results indicates that subgap defect states enclosed by E=0.82 eV and Ef are the dominant recombination centers.

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