Defect Creation by Forward Bias in Amorphous Silicon P-I-N Diodes

1991 ◽  
Vol 219 ◽  
Author(s):  
R. A. Street ◽  
M. Hack
Keyword(s):  
Temperature Dependence ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Forward Bias ◽  
Bias Current ◽  
Square Root ◽  
Weak Temperature Dependence ◽  
Defect Creation ◽  
Defect Densities

ABSTRACTMetastable defects are induced in a-Si:H p-i-n devices by a forward bias current. The defect density increases approximately as the square root of time, reaching saturation at long inducing times, and with a weak temperature dependence. Current-induced defect annihilation is observed, in which the current causes a reduction in the previously induced defect density. Calculations of the changes in the forward bias current for different bulk defect densities are able to account for the measured results.

Comparison of Current and Light Induced Defects in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A. Street ◽  
W.B. Jackson ◽  
M. Hack
Keyword(s):  
Numerical Modelling ◽  
Reverse Bias ◽  
Defect Density ◽  
Reverse Current ◽  
Bias Current ◽  
Spatial Profile ◽  
Forward Current ◽  
Defect Creation ◽  
Induced Defects ◽  
Metastable Defect

Metastable defect creation by illumination and by a forward current in p-i-n devices are compared using CPM and reverse current measurements of the defect density. The data show that the same defects are formed by the two mechanisms, but with different spatial profiles. Numerical modelling shows how the spatial profile influences the reverse bias current.

Saturation behavior of the Light-Induced Defect Density in Hydrogenated Amorphous Silicon

1990 ◽  
Vol 192 ◽  
Author(s):  
H. R. Park ◽  
J. Z. Liu ◽  
P. Roca i Cabarrocas ◽  
A. Maruyama ◽  
M. Isomura ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Room Temperature ◽  
Urbach Energy ◽  
Defect Density ◽  
Generation Rate ◽  
Carrier Generation ◽  
Defect Generation ◽  
Ion Laser ◽  
Hydrogenated Amorphous ◽  
Defect Densities

ABSTRACTUsing a Kr ion laser (λ = 647.1 nm) to produce a carrier generation rate G of 3 × 1020 cm−3s−1, we have saturated the light-induced defect generation in hydrogenated (and fluorinated) amorphous silicon (a-Si:H(F)), within a few hours near room temperature. While the defect generation rate scales roughly with 1/G2, the saturation defect densities Ns,sat are essentially independent of G. The saturation is not due to thermal annealing. We have further measured Ns,sat m 37 a-Si:H(F) films grown in six different reactors under different conditions. The results show that Ns,sat lies between 5 × 1016 and 2 × 1017 cm−3, that Ns,sat drops with decreasing optical gap and hydrogen content, and that Ns,sat is not correlated with the initial defect density or with the Urbach energy.

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.

Simulation of Quantum Efficiency Spectroscopy for Amorphous Silicon P-I-N Junctions

1999 ◽  
Vol 557 ◽  
Author(s):  
Rodney Estwick ◽  
Vikram L. Dalal
Keyword(s):  
Electric Field ◽  
Amorphous Silicon ◽  
Quantum Efficiency ◽  
Applied Voltage ◽  
Forward Bias ◽  
Hole Mobility ◽  
Limited Range ◽  
D Model ◽  
Defect Densities ◽  
Minority Carriers

AbstractQuantum efficiency(QE) spectroscopy of amorphous silicon and alloy solar cells has been used for many years now to determine the mobility-lifetime products for minority carriers. Similarly, matching of I(V) curves, assuming a linear model for collection as a function of applied voltage, has been used to quantify the effects of degradation on cell performance by estimating changes in the collection length [or range] of holes. In this paper, we do a numerical simulation of these techniques, using the AMPS I-D model developed by Fonash and his coworkers. The simulation shows that neither the lifetime nor the electric field in the devices is constant as a function of position. Nor is the electric field a linear function of applied voltage, particularly when the voltage exceeds about half the built-in voltage. The uniformity of the lifetime depends on the applied bias and on the defect densities in the material. This variation in electric field and lifetime and nonlinearity with applied voltage makes questionable some of the conclusions drawn from fitting device I(V) curves, particularly under forward bias. However, when one uses only a limited range of forward bias, or, preferably, make measurements in cells with thicker i layers under reverse bias, one c.an make reasonable estimates of the hole mobility-lifetime(μτ) product or the collection lengthl The simulations also show that indeed, it is the hole μτ product which is the limiting parameter.

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.

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.

Experimental Determination for the Transition Temperature Between Ballistic and Hopping Controlled Recombination in a-Si:H

1990 ◽  
Vol 192 ◽  
Author(s):  
M. E. Zvanut ◽  
K. Wang ◽  
D. Han ◽  
M. Silver
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Experimental Determination ◽  
Transit Time ◽  
Carrier Lifetime ◽  
Characteristic Temperature ◽  
Forward Bias ◽  
Bias Current ◽  
Current Increase ◽  
Substantial Rise

ABSTRACTThe transient forward bias current of a-SI:H p-i-n diodes has been measured as a function of temperature and voltage. The transient shows an initial decay followed by a substantial rise which suggests a large value for the ratio of the carrier lifetime to the transit time as demonstrated by Shapiro. We found that both the time at which the rise begins and the ratio of the final saturated current to the minimum current increase with decreasing temperature for temperature greater than a characteristic temperature, Tc. For T < Tc, both the time and the ratio abruptly decrease with temperature. We attribute this change in temperature dependence to a change in the transport kinetics from ballistic to hopping controlled recombination.

VLSI Processing of Amorphous Silicon Alloy P-I-N Diodes For Active Matrix Applications

1986 ◽  
Vol 70 ◽  
Author(s):  
J. McGill ◽  
V. Cannella ◽  
Z. Yaniv ◽  
P. Day ◽  
M. Vijan
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Current Density ◽  
Reverse Bias ◽  
Unit Area ◽  
Forward Bias ◽  
Bias Current ◽  
Active Matrix ◽  
Silicon Alloy ◽  
Current Densities

ABSTRACTA number of new amorphous silicon alloy microelectronic devices, including LCD active matrix displays, linear image sensors, and thin film multilayer computer memories, have been developed in our company. These applications rely heavily on the quality of the intrinsic semiconductor as well as its ability to withstand the many processing steps used in a modern photolithographic process. In this paper, we present electrical data on amorphous silicon alloy p-i-n diodes after such a process. These devices have an active area of 20μm × 20μm defined using standard photolithographic techniques and etched using a dry etch process. These diodes are characterized by ideality factors (n) of 1.4 and extrapolated reverse saturation current densities of 1013A/cm2h. The diodes exhibit nearly 10 orders of magnitude rectification at ± 3V and the reverse bias current density remains below 10-8 A/cm2 for reverse bias voltages of -15V. In pulsed forward bias, these diodes can be operated at current densities greater than 300A/cm2. Thin film amorphous silicon diodes moreover have the advantage that varying the thickness of the intrinsic layer allows the optimization of parameters such as the capacitance per unit area, the reverse bias current density and the forward bias conductance per unit area. We find that these devices are fully compatible with state of the art VLSI processing techniques and are suitable for applications in integrated circuit structures, for example rectification devices in microelectronic arrays and isolation devices in display matrices.

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