Capacitance Studies of Light-Induced Effects in Undoped Hydrogenated Amorphous Silicon

1985 ◽  
Vol 49 ◽  
Author(s):  
K. Zellama ◽  
J.D. Cohen ◽  
J.P. Harbison
Keyword(s):  
Electrical Conductivity ◽  
Amorphous Silicon ◽  
Density Of States ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Light Saturation ◽  
Band Tail ◽  
Bond Density ◽  
Induced Changes ◽  
Hydrogenated Amorphous

AbstractThe effects of light saturation on the properties of undoped a-Si:H films were studied by a new capacitance profiling technique which can be used to directly determine changes in the dangling bond density of states near midgap. Coplanar conductivity and capacitance vs. temperature measurements save the changes in activation energies for electrical conductivity. These studies indicate that, while substantial increases in the dangling bond densities are observed for most samples, the detailed behavior of the light induced changes in these films are inconsistent with the creation of such defects by breaking weak valence band tail states.

Inadequacy of the Conventional View of Hydrogenated Amorphous Silicon

1986 ◽  
Vol 70 ◽  
Author(s):  
D. Adler ◽  
M. Silver ◽  
M. P. Shaw ◽  
V. Cannella
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Intrinsic Defect ◽  
Dangling Bond ◽  
Defect States ◽  
Band Tail ◽  
Conventional View ◽  
Substitutional Doping ◽  
Hydrogenated Amorphous ◽  
Basic Experimental Data

ABSTRACTThe conventional view of the electronic structure of hydrogenated amorphous silicon is: (1) the material is characterized by a mobility gap of about 1.8 eV, with exponential band tails due to disorder and deep defect states arising from silicon dangling bonds (T3 centers); (2) substitutional doping occurs because of the formation of chargedimpurity/dangling-bond pairs, e.g. P4+ – T3-, at the substrate temperature; (3) the effective correlation of the T3 center is about 0.4 eV; (4) T3o centers are the predominant recombination center; (5) the three intrinsic ESR signals are due to electrons on T3o centers, electrons in the conduction band tail, and holes in the valence band tail. It is the purpose of this paper to demonstrate that this model is in sharp disagreement with an array of basic experimental data, and much of the evidence presented in its favor is based on self-inconsistent logic. We conclude that it is very likely that large concentrations of charged intrinsic defect pairs are present in all hydrogenated amorphous silicon films.

scholarly journals Material Parameters in a Thick Hydrogenated Amorphous Silicon Detector and their Effect on Signal Collection

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Qureshi ◽  
V. Perez-Mendez ◽  
S. N. Kaplan ◽  
I. Fujieda ◽  
G. Cho
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Detector ◽  
Dangling Bond ◽  
Material Parameters ◽  
Bond Density ◽  
Transient Photoconductivity ◽  
Signal Collection ◽  
Hydrogenated Amorphous

ABSTRACTTransient photoconductivity and ESR measurements were done to relate the ionized dangling bond density and the spin density of thick hydrogenated amorphous silicon (a-Si:H) detectors. We found that only a fraction (∼30–35%) of the total defect density as measured by ESR is ionized when the detector is biased into deep depletion. The measurements on annealed samples also show that this fraction is about 0.3. An explanation based on the shift of the Fermi energy is given. The measurements show that the time dependence of relaxation is a stretched exponential.

Mechanical Spectroscopy Study on the Light Soaking Effect on Hydrogenated Amorphous Silicon

2012 ◽  
Vol 184 ◽  
pp. 416-421 ◽  
Author(s):  
H. Mizubayashi ◽  
I. Sakata ◽  
H. Tanimoto
Keyword(s):  
Internal Friction ◽  
Temperature Dependence ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Wide Distribution ◽  
Activation Energies ◽  
Mechanical Spectroscopy ◽  
Induced Changes ◽  
Mild Temperature ◽  
Hydrogenated Amorphous

For hydrogenated amorphous silicon (a-Si:H) films deposited at temperatures between 423 K and 623 K (a-Si:H423Kand so on), the light-induced changes in the internal friction between 80 K and 400 K were studied. The internal friction is associated with H2motion in microvoid networks, and shows the mild temperature dependence between about 80 K and 300 K (Q-180-300K) and the almost linear increase above 300 K (Q-1>300K). BothQ-180-300KandQ-1>300Kdecrease with increasing the deposition temperature, and show the mild temperature dependence ina-Si:H623K. The white light soaking with 100 mW/cm2(WLS100and so on) below 300 K caused a change inQ-180-300Kand no changes inQ-1>300K, respectively, and the light-induced changes inQ-180-300Krecovered after annealing at 423 K. The wide distribution of activation energies for H2motions between microvoids indicate that most of neighboring microvoids are connected through windows, i.e., the microvoid networks are existing ina-Si:H, and the spatially loose or solid structures are responsible for the low or high activation energies for the H2motion between microvoids, respectively. Furthermore, the light-induced hydrogen evolution (LIHE) was observed for WLS200to WLS400in a vacuum between 400 and 500 K, resulting in the disappearance of the internal friction due to the H2motion in the microvoid network.

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