Time-of-Flight Measurements in a-Si:H Between Room Temperature and 130° C°

1987 ◽  
Vol 95 ◽  
Author(s):  
D. S. Shen ◽  
S. Aljishi ◽  
Z E. Smith ◽  
J. P. Conde ◽  
V. Chu ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Room Temperature ◽  
Time Of Flight ◽  
High Sensitivity ◽  
Drift Mobility ◽  
Hole Transport ◽  
Dispersive Transport ◽  
Band Tail ◽  
Flight Measurements

AbstractThe drift mobility μd and the mobility-lifetime product μτ in undoped a-Si:H have been studied up to 130°C. The electron μde is temperature-activated with Eae = 0.13 to 0.16 eV. The electron (μτ)e increases with temperature T. For hole transport, we observe the transition from dispersive to non-dispersive transport with increasing T. The hole μdh is ∼ 1/100 of μde, and is activated with Eah = 0.34 to 0.48eV. The hole (μτ)h does not change much with T. A computer simulation demonstrates the high sensitivity of μd to the band tail width.

Transport Properties of Compensated μc-Si:H

1996 ◽  
Vol 420 ◽  
Author(s):  
N. Wyrsch ◽  
M. Goerlitzer ◽  
N. Beck ◽  
J. Meier ◽  
A. Shah
Keyword(s):  
Transport Properties ◽  
Room Temperature ◽  
Time Of Flight ◽  
Drift Mobility ◽  
Hole Transport ◽  
Microcrystalline Silicon ◽  
Dispersive Transport ◽  
Experimental Values ◽  
First Time ◽  
Photovoltaic Material

AbstractElectron and hole transport in completely microcrystalline silicon (μc-Si) p-i-n cells and in intrinsic or near intrinsic μc-Si layers have been investigated, for the first time, by time of flight (TOF) at temperatures between 100 and 400 K.At room temperature, both electron and hole drift mobilities were found to be between 0.2 and 1 cm2 V-ls-1. No trace of anomalous dispersive transport was observed, neither for electrons nor for holes, down to 100 K. A decrease of the drift mobility was observed when the temperature was raised from room temperature to 400 K as usually observed in crystalline semiconductors. However, these experimental values of the drift mobilities appear more puzzling than helpful for the comprehension of this “new” photovoltaic material.

Comments on Electron and Hole Transport in the Band Tail States of Amorphous Silicon at Low Temperatures

1989 ◽  
Vol 149 ◽  
Author(s):  
M. Silver ◽  
W. E. Spear
Keyword(s):  
Amorphous Silicon ◽  
Drift Mobility ◽  
Hole Transport ◽  
Experimental Results ◽  
Exponential Tail ◽  
Band Tail ◽  
State Distribution ◽  
Temperature Drift ◽  
Model Calculations ◽  
Tail State

ABSTRACTRecent experimental results on the low temperature drift mobility in amorphous silicon are examined on the basis of the approach to hopping transport developed by Silver and Bässler. It is shown on general grounds that the main features of the experimental results cannot be explained by a purely exponential tail state distribution, but are consistent with the distribution used by Spear and Cloude (1988) in model calculations.

scholarly journals Optical and Electrical Properties of Undoped Microcrystalline Silicon Deposited by the VHF-GD with Different Dilutions of Silane in Hydrogen

1996 ◽  
Vol 452 ◽  
Author(s):  
N. Beck ◽  
P. Orres ◽  
J. Fric ◽  
Z. Remeš ◽  
A. Poruba ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Room Temperature ◽  
Crystalline Silicon ◽  
Time Of Flight ◽  
Optical And Electrical Properties ◽  
Microcrystalline Silicon ◽  
Transient Time ◽  
Deep Traps ◽  
Flight Measurements ◽  
Strong Dilution

AbstractWe show that the optical and electrical properties of microcrystalline silicon (μc-Si:H) deposited by the VHF-GD technique at 110 MHz can considerably be tuned by changing the dilution ratio of silane to hydrogen.With increasing silane dilution we observe enhanced optical absorption for energies below 2 eV due to the transition of the material from amorphous / microcrystalline mixture to a pure microcrystalline phase. Simultaneously, the light scattering and the defect absorption increases. Strong dilution also promotes the incorporation of impurities into the material, leading to a pronounced extrinsic behaviour as seen from the decrease of the activiation energy of the electrical conductivity.The electrical properties were investigated in the dark by the Time of Flight technique. We measured drift mobilities at room temperature which slightly increase with dilution, reaching values of 3 cm2/Vs for electrons and 1.2 cm2/Vs for holes. The ratio between electron and hole drift mobilities is found to be around 2 for all samples studied, similar to that of crystalline silicon.Furthermore, post-transient Time of Flight measurements revealed detrimental electron deep traps in low dilution material.

Time-of-Flight Measurement on a-Ge:H and a-SiGe:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
E.Z. Liu ◽  
D. Pang ◽  
W. Paul ◽  
J.H. Chen
Keyword(s):  
Room Temperature ◽  
Transport Model ◽  
Drift Mobility ◽  
Band Tail ◽  
High Quality ◽  
Hopping Transport ◽  
Flight Measurement ◽  
Order Of Magnitude ◽  
Temperature Ranges ◽  
Electron Drift Mobility

ABSTRACTWe report TOF measurements on high quality intrinsic a-Ge:H and a-SiGe:H films of E04=1–4.eV in temperature ranges of 200 to 280 and 230 to 300K, respectively. Complete charge collection is achieved in all measurements. For a-Ge:H films, the (μτ)e product obtained from the Hecht plot is (5±3)×10-8 cm2/V above 240K and decreases at lower temperatures. The electron transit signal is dispersive at all temperatures. The a obtained from ttV-1/αis 0.23 at 200K and approaches 1.0 at 260K. The electron drift mobility μd shows activated behavior, with an energy of 0.37±0.05eV, and has an extrapolated room temperature value of 0.03 cm2/Vs. Compared to a-Ge:H, μd of a-SiGe:H alloy samples is lower by one order of magnitude but has a similar activation energy. These results are consistent with a band tail hopping transport model.

A Novel Preparation Technique Termed “Chemical Annealing” to make a Rigid and Stable Si-Network

1991 ◽  
Vol 219 ◽  
Author(s):  
Hajime Shirai ◽  
Jun-Ichi Hanna ◽  
Isamu Shimizu
Keyword(s):  
Atomic Hydrogen ◽  
Room Temperature ◽  
Drift Mobility ◽  
Preparation Technique ◽  
Dispersive Transport ◽  
Optical Gap ◽  
Chemical Annealing ◽  
Flight Measurement ◽  
The Stability

ABSTRACTA novel preparation technique termed “Chemical Annealing (CA)” was developed with aim of making a stable and rigid structure of Si-network. The a-Si:H films were made by the alternate deposition of several tens angstrom thick a-Si:H and the treatment with atomic hydrogen or excited novel gases such as Ar* and He*. Hydrogen contents (CH) and optical gap (Eg) in the film prepared by this tecnique were able to reduced by CH of 1.5at%, and Eg of 1.5eV, respectively at substrate temperature:300C. All of them exhibited high photoconductivities in the level of 10-5 10-4 S/cm under illumination of 100mW/cm2. In the films with CH of 3at% or less, in particular, marked improvement was confirmed in the stability after light soaking. In addition, the time-of-flight measurement revealed a non-dispersive transport and a significant enhancement in the drift mobility of holes up to 0.2cmm2/Vs at room temperature in the film with CH : 5at% and Eg:1.65eV prepared at 300C. Advantages of the CA process are summarized together with the discussion of role of atomic hydrogen, excited novel gases such as Ar* and He* in the growing surface.

Time-of-flight study of electrical charge mobilities in liquid-crystalline zinc octakis(β-octoxyethyl) porphyrin films

2000 ◽  
Vol 15 (11) ◽  
pp. 2494-2498 ◽  
Author(s):  
Yang Yuan ◽  
Brian A. Gregg ◽  
Marcus F. Lawrence
Keyword(s):  
Charge Transport ◽  
Liquid Crystalline ◽  
Room Temperature ◽  
Thick Films ◽  
Time Of Flight ◽  
Charge Carriers ◽  
Electrical Charge ◽  
Charged Carrier ◽  
Flight Measurements ◽  
Discotic Mesophase

Time-of-flight measurements performed on micron-thick films of liquid-crystalline zinc octakis(β-octoxyethyl) porphyrin indicated that charge carriers possess significantly high drift mobilities, attaining approximately 0.01 cm2 V−1s −1 and 0.008 cm2 V−1s −1 for holes and electrons, respectively, at room temperature. Upon heating the samples from 300 to 420 K, causing the porphyrin to go from the solid-crystalline to the discotic mesophase, the mobilities did not decrease drastically, and remained at values slightly larger than half those observed at room temperature. Charge transport in this material conformed to the Scher–Montroll model, which attributes a distribution of hopping times to the propagation of the initially formed charged carrier packet. Analysis of the “universal” plots prescribed by this model yielded a dispersion factor of 0.5 for both charge carriers.

scholarly journals Holographic time-of-flight measurements of the hole-drift mobility in a photorefractive polymer

1995 ◽  
Vol 52 (20) ◽  
pp. R14324-R14327 ◽  
Author(s):  
G. G. Malliaras ◽  
V. V. Krasnikov ◽  
H. J. Bolink ◽  
G. Hadziioannou
Keyword(s):  
Time Of Flight ◽  
Drift Mobility ◽  
Photorefractive Polymer ◽  
Flight Measurements

Control of the Electron and Hole Drift mobilities in Plasma Deposited a-Si:H

1994 ◽  
Vol 336 ◽  
Author(s):  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Room Temperature ◽  
Film Growth ◽  
Drift Mobility ◽  
Growth Surface ◽  
Band Tail ◽  
Capacitively Coupled ◽  
Deposition Parameters ◽  
Optimum Energy ◽  
Temperature Dependences ◽  
Stimulation Of

ABSTRACTThe ‘time-of-flight’ technique measured electron and hole drift mobilities are shown to be independent of deposition parameters in capacitively coupled, diode type RF-PECVD a-Si:H. However, the carrier mobilities can be varied by orders of magnitude by changing the bias applied to the mesh type controlling electrode in a triode type reactor. The room temperature hole drift mobility increases to 10−1cm2/Vs when an appropriate bias is applied to the mesh providing optimum energy ion stimulation of the film growth surface during deposition. Analysis of the field and temperature dependences of the drift mobilities shows that in the best specimens the conduction (valence) band tail density of states are approximately exponential with a reciprocal slope of lOMeV (25MeV).

Sign in / Sign up

Export Citation Format

Share Document