A Critical Test of Defect Creation Models in Hydrogenated Amorphous Silicon Alloys

2000 ◽  
Vol 609 ◽  
Author(s):  
Kimon C. Palinginis ◽  
Jeffrey C. Yang ◽  
S. Guha ◽  
J. David Cohen
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Dangling Bonds ◽  
Silicon Alloys ◽  
Illumination Time ◽  
Deep Defect ◽  
Photocurrent Spectroscopy ◽  
Defect Creation ◽  
The Creation ◽  
Kinetics Of

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.

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.

Dynamics of the creation of light-induced defects in amorphous silicon alloys

1986 ◽  
Vol 33 (4) ◽  
pp. 2512-2519 ◽  
Author(s):  
M. Hack ◽  
S. Guha ◽  
W. den Boer
Keyword(s):  
Amorphous Silicon ◽  
Silicon Alloys ◽  
The Creation ◽  
Induced Defects

Annealing Kinetics of Amorphous Silicon Alloy Solar Cells Made at Various Deposition Rates

2001 ◽  
Vol 664 ◽  
Author(s):  
Baojie Yana ◽  
Jeffrey Yanga ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
High Frequency ◽  
Room Temperature ◽  
Defect Density ◽  
Very High Frequency ◽  
Solar Cell Performance ◽  
Kinetics Of ◽  
Very High

ABSTRACTA systematic study has been made of the annealing kinetics of amorphous silicon (a-Si) alloy solar cells. The cells were deposited at various rates using H2 dilution with radio frequency (RF) and modified very high frequency (MVHF) glow discharge. In order to minimize the effect of annealing during light soaking, the solar cells were degraded under 30 suns at room temperature to quickly reach their saturated states. The samples were then annealed at an elevated temperature. The J-V characteristics were recorded as a function of annealing time. The correlation of solar cell performance and defect density in the intrinsic layer was obtained by computer simulation. Finally, the annealing activation energy distribution (Ea) was deduced by fitting the experimental data to a theoretical model. The results show that the RF low rate solar cell with high H2 dilution has the lowest Ea and the narrowest distribution, while the RF cell with no H2 dilution has the highest Ea and the broadest distribution. The MVHF cell made at 8Å/s withhigh H2 dilution shows a lower Ea and a narrower distribution than the RF cell made at 3 Å/s, despite the higher rate. We conclude that different annealing kinetics plays an important role in determining the stabilized performance of a-Si alloy solar cells.

The Role of Charged Defects In Current Transport Through Hydrogenated Amorphous Silicon Alloys

1998 ◽  
Vol 507 ◽  
Author(s):  
S.P. Lau ◽  
J.M. Shannon ◽  
B.J. Sealy ◽  
J.M. Marshall
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Current Transport ◽  
Dangling Bond ◽  
Silicon Alloys ◽  
Metal Structures ◽  
Bond State ◽  
Donor States ◽  
Charged Defects

ABSTRACTCurrent transport in metal-semiconductor-metal structures based on amorphous silicon alloys has been studied in relation to the density of dangling bond state defects. The density of defects was changed by varying alloy composition or by current stressing. We show that the change of current-voltage characteristics and activation energy with defect density and the onset of Poole-Frenkel conduction with composition require charged defects. It is found that there are more charged defects in amorphous silicon nitride (a-Si1−xNx:H) than in amorphous silicon carbide (a-Si1−xCx:H). In addition, an excess of negatively charged dangling bond defects compared to positively charged dangling bond defects is observed in a-Si1−xNx:H films. This is attributed to the presence of N4+ act as the donor states in silicon nitride. We find that the density of charged dangling bond defects can be higher than 1019cm−3.

Correlation between film and cell properties for DC plasma deposited amorphous silicon

2001 ◽  
Vol 664 ◽  
Author(s):  
Jennifer Heath ◽  
Suman B. Iyer ◽  
Yoram Lubianiker ◽  
J. David Cohen ◽  
Gautam Ganguly
Keyword(s):  
Growth Rate ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Silicon Film ◽  
Device Performance ◽  
Solar Cell Device ◽  
Film Properties ◽  
Dc Plasma ◽  
Hydrogen Dilution ◽  
Photocurrent Spectroscopy

ABSTRACTWe have carried out measurements to try to correlate amorphous silicon film properties with companion solar cell device performance. The dc plasma deposited intrinsic films were prepared with various hydrogen dilution levels, and increasing power levels to increase growth rate. The electronic properties were determined using admittance spectroscopy and drive-level capacitance profiling (DLCP) techniques as well as transient photocapacitance and photocurrent spectroscopy. Cell and film performance were explored in both as-grown and light-soaked states. We observed that, although cell performance decreased systematiclly with increasing growth rate, it depended on factors other than the deep defect density in the matched films. On the other hand, we did observe that increases in defect density caused by the light-induced degradation led to fairly predictable decreases in the cell fill factors.

Evidence For Trap-Conversion Induced Instability In Amorphous Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
Vikram L. Dalal ◽  
Puneet Sharma ◽  
Abdul Aziz
Keyword(s):  
Energy Range ◽  
Amorphous Silicon ◽  
Photon Energy ◽  
Correlation Energy ◽  
Early Time ◽  
Photon Energy Range ◽  
Dangling Bonds ◽  
Defect States ◽  
Conversion Model ◽  
Kinetics Of

AbstractIt has been shown recently that there are two distinct types of recovery during annealing of amorphous Silicon after degradation due to light soaking. It has been postulated that the two different kinetics of annealing point to the existence of two different types of states, with perhaps one state being charged dangling bonds and the other state being neutral dangling bonds. To see if two kinds of states exist, in this paper, we study the kinetics of degradation within the first 100 seconds, and also study the entire absorption curve at all degradation times. An analytical model is derived for early time degradation based on the conversion of a D- state into a neutral dangling band by absorption of a light generated ( the trap-to-dangling bond conversion model of Adler) and the experimental data of degradation versus light intensity fit the predictions of the model very well. The model also predicts that the Adler-type negatively charged defect states, which have a negative correlation energy, upon conversion will transform into Do states at a higher energy, and therefore, there should be a decrease in absorption corresponding to states closer to the valence band, and an increase in absorption corresponding to states near the mid-gap. For the films where such D- states are deliberately introduced by using a small oxygen (a donor atom) leak, we see strong evidence for such a behavior in absorption, with a decrease in the 1.3-1.4 eV photon energy range, and an increase in the 1.1 eV photon energy range. The increase in Do corresponds well with the decrease in photo-conductivity, even at the earliest times.

Nature of Charged Metastable Defects in Network Rebonding Model

2002 ◽  
Vol 715 ◽  
Author(s):  
R. Biswas ◽  
B. C. Pan
Keyword(s):  
Low Temperature ◽  
Rate Equations ◽  
Atomistic Model ◽  
Dangling Bonds ◽  
Defect Creation ◽  
Higher Temperature ◽  
Kinetics Of Degradation ◽  
Kinetics Of ◽  
Defect Densities ◽  
Positively Charged

AbstractWe recently developed an atomistic model of metastability of a-Si:H, where defect creation is driven by the breaking of weak silicon bonds. The kinetics of degradation in this model is simulated with coupled rate equations that show t1/3 kinetics of defect creation and saturation behavior similar to experiment. Saturated defect densities of neutral dangling bonds are accompanied by a much smaller density of negatively charged floating bonds and positively charged dangling bonds (D+). We propose a two-step annealing mechanism where the positively charged D+ dangling bonds are annealed at low temperature and the D0 at higher temperature -which accounts for hysteresis in mobility lifetime products.

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