Pulsed-Light-Induced Metastable Defect Creation in Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
Jong-Hwan Yoon ◽  
H. L. Kim
Keyword(s):  
Time Dependence ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Pulsed Light ◽  
Illumination Time ◽  
Defect Creation ◽  
Annealing Rate ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTWe report the results of a study of metastable defect creation by pulsed light soaking in undoped hydrogenated amorphous silicon (a-Si:H). An illumination time dependence of the defect density, a saturated defect density, and light-induced annealing under pulsed laser light have been studied. Measurements show approximately a t1/2 time-dependence of the defect creation, which is independent of light intensity. It is observed that the saturation value of the defect density is about one order of magnitude higher than by cw illumination in device quality films. It has been suggested that these results would be due to the difference in the light-induced defect annealing rate between cw and pulsed lights, in which it is found that the light-induced annealing rate by pulsed light is lower than by cw light.

Saturation of the defect density in hydrogenated amorphous silicon by pulsed light soaking

1992 ◽  
Vol 61 (15) ◽  
pp. 1817-1819 ◽  
Author(s):  
Nobuhiro Hata ◽  
Gautam Ganguly ◽  
Sigurd Wagner ◽  
Akihisa Matsuda
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Pulsed Light ◽  
Hydrogenated Amorphous

Dispersive Hydrogen Motion and Creation of Light-Induced Defects in Hydrogenated Amorphous Silicon

1989 ◽  
Vol 149 ◽  
Author(s):  
W. B. Jackson
Keyword(s):  
Kinetic Equation ◽  
Temperature Dependence ◽  
Amorphous Silicon ◽  
Hydrogen Diffusion ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Illumination Time ◽  
Induced Defects ◽  
Hydrogenated Amorphous ◽  
Creation Rate

ABSTRACTThis paper investigates the application of the dispersive hydrogen diffusion defect kinetic equation for the generation of light-induced defects. Self-limited monomolecular carrier defect generation by dispersive motion can explain the observed t1/3 and the G0.6 dependence where t is the illumination time and G is the illumination intensity as well as the equilibrium defect density as a function of temperature. However, the temperature dependence of the creation rate and compatibility with current degradation experiments remain unresolved problems.

Polarized Electroabsorption in Pulse and Continuous Light-Soaked a-Si:H - Structural Change other than Defect Creation

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Hata ◽  
T. Kamei ◽  
H. Okamoto ◽  
A. Matsuda
Keyword(s):  
Structural Change ◽  
Amorphous Silicon ◽  
Annealing Time ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Continuous Light ◽  
Laser Pulses ◽  
Defect Creation ◽  
Short Time ◽  
Hydrogenated Amorphous

ABSTRACTExperimental results on structural change other than defect creation upon light-soaking of hydrogenated amorphous silicon (a-Si:H) are reported. A-Si:H films were light-soaked with laser pulses or with continuous (cw) light to steady-states, and then annealed at 170 °C in vacuum. The changes in electro-absorption (EA) signal, and defect density (Nd) from subgap absorption were measured as functions of light-soaking/annealing time. The results are: (1) EA ratio, which is defined as the ratio of anisotropie to isotropie components in EA signal, increases upon light-soaking with a time constant shorter by almost two orders of magnitude than that for Nd increase, and (2) shows saturation when extensively light-soaked. (3) The saturated values of EA ratio are comparable for both pulsed and cw light-soaking. (4) Both the EA ratio and Nd show recovery to the values in the annealed states. It is suggested that light-soaking causes a structural change in a short time, as manifested by EA ratio, and this changed structure works as the pathway leading to the defect creation. Thermal annealing is also discussed.

Photoinduced Expansion in Hydrogenated Amorphous Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
S. Nonomura ◽  
T. Gotoh ◽  
M. Nishio ◽  
T. Sakamoto ◽  
M Kondo ◽  
...  
Keyword(s):  
Time Dependence ◽  
Amorphous Silicon ◽  
Volume Change ◽  
Chalcogenide Glasses ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Structural Aspect ◽  
Photothermal Effect ◽  
Preparation Conditions ◽  
Hydrogenated Amorphous

AbstractThe structural aspect of photodegradation effect in hydrogenated amorphous silicon has been investigated by the use of the simple and sensitive detection technique, the laser optical-lever bending method, for a small expansion or extraction in thin films. The volume change induced by the thermal expansion due to the photothermal effect and the residual expansion was observed in hydrogenated amorphous silicon prepared by PECVD. The latter residual expansion was persistent after light soaking and was recovered by thermal annealing at 200°C.The time dependence of the volume expansion with light soaking shows the same time dependence of photoinduced defect density. The photoinduced volume changes normalized by the initial volume are the order of 10-5~10-5, which values are two orders smaller than chalcogenide glasses such as a-As2S3. The normalized volume change of a-Si:H with the different sample preparation conditions of PECVD such as the hydrogen dilution ratio r (r = SiH4/H2) and substrate temperature is shown. Also it is demonstrated that the photoinduced expansion is observed in hydrogenated amorphous silicon prepared by photo CVD and hot-wire CVD methods. The spatial extent related to a photoinduced defect creation in a-Si:H is estimated.

Capacitance Studies of Metastable Defect Creation in Hydrogenated Amorphous Silicon

1986 ◽  
Vol 70 ◽  
Author(s):  
J. D. Cohen ◽  
K. Mahavadi ◽  
K. Zellama ◽  
J. P. Harbison ◽  
A. E. Delahoy
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Microscopic Models ◽  
Deep State ◽  
Absorption Studies ◽  
Defect Creation ◽  
Metastable Effects ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTWe have studied the light induced instability problem in hydrogenated amorphous silicon using junction capacitance techniques. These techniques are used to examine specific changes in the density of gap states, and occupation of gap states, for undoped a-Si:H samples after light saturation and for a series of partial anneal “states” which culminate in the original dark annealed state (state A). We find that the observed changes in the metastable occupied and unoccupied defects contradict the Si-Si bond breaking model and indicate at least two defect creation processes. In several samples we also find clear evidence that the metastable defect distribution near midgap has a slightly different energy distribution than the stable deep state (dangling bond) distribution. At the same time, these results seem to be qualitatively consistent with many aspects of recent ESR and optical absorption studies of metastable defect creation. We discuss these findings in terms of alternative possible microscopic models for metastable effects in a-Si:H.

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