A-Si:H Ambipolar Diffusion Length and Effective Lifetime Measured by Flying Spot Technique (FST)

1991 ◽  
Vol 219 ◽  
Author(s):  
M. Vieira ◽  
R. Martins ◽  
E. Fortunato ◽  
F. Soares ◽  
L. Guimaraes
Keyword(s):  
Laser Beam ◽  
Transient Analysis ◽  
Diffusion Length ◽  
Transport Equations ◽  
Ambipolar Diffusion ◽  
Schottky Barriers ◽  
Effective Lifetime ◽  
Asymmetrical Distribution ◽  
Flying Spot

ABSTRACTThe determination of the ambipolar diffusion length, L*, and the effective lifetime, τ*, in p/i and a-Si:H Schottky barriers (ITO/p/a-Si:H/Al-Si; Cr/a-Si:H/Cr/Ag) have been determined by Flying Spot Technique, FST. This technique consists in the transient analysis of the photocurrent/photopotential induced by a laser beam that moves perpendicularly to the structure with a constant motion ratio, at different velocities. Taking into account the competition between the diffusion/drift velocities of the excess carriers and the velocity of the flying spot, it is possible to solve the transport equations and to compute separately L* and τ*, from the asymmetrical distribution responses.

A General Analysis of Steady State Photocarrier Grating Technique for the Determination of Ambipolar Diffusion Length

1990 ◽  
Vol 192 ◽  
Author(s):  
Yuan-Min Li
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Dielectric Relaxation ◽  
General Formula ◽  
Applied Electric Field ◽  
Diffusion Length ◽  
Ambipolar Diffusion ◽  
General Analysis

ABSTRACTA general photoconductivity formula is derived for the case of a semiconductor steady state photocarrier grating (SSPG)1. It is shown that, under the condition of weak applied electric field, the ambipolar diffusion length can be determined by the SSPG technique1without the lifetime-regime restriction2,3 if the lifetime of photocarriers is known. The general formula presented here is reduced to the simple lifetime-regime formula1–3 under the condition of fast dielectric relaxation.

scholarly journals Determination of electron diffusion length in HgCdTe photodiodes using laser beam induced current

2009 ◽  
Vol 58 (11) ◽  
pp. 7884
Author(s):  
Yin Fei ◽  
Hu Wei-Da ◽  
Quan Zhi-Jue ◽  
Zhang Bo ◽  
Hu Xiao-Ning ◽  
...  
Keyword(s):  
Laser Beam ◽  
Diffusion Length ◽  
Induced Current ◽  
Electron Diffusion ◽  
Electron Diffusion Length ◽  
Hgcdte Photodiodes

scholarly journals Direct determination of the ambipolar diffusion length in GaAs/AlGaAs heterostructures by cathodoluminescence

1989 ◽  
Vol 55 (16) ◽  
pp. 1647-1649 ◽  
Author(s):  
H. A. Zarem ◽  
P. C. Sercel ◽  
J. A. Lebens ◽  
L. E. Eng ◽  
A. Yariv ◽  
...  
Keyword(s):  
Diffusion Length ◽  
Direct Determination ◽  
Ambipolar Diffusion

Determination of a-Si:H Film Quality Throughfst and Sclc Techniques

1990 ◽  
Vol 192 ◽  
Author(s):  
R. Martins ◽  
M. Vieira ◽  
E. Fortunato ◽  
I. Ferreira ◽  
F. Soares ◽  
...  
Keyword(s):  
Diffusion Length ◽  
Surface Effect ◽  
Schottky Diodes ◽  
Effective Diffusion ◽  
Effective Lifetime ◽  
Thermally Activated ◽  
Best Parameter ◽  
And Diffusion ◽  
High Photosensitivity

ABSTRACTThe ambipolar diffusion length (L*) and the effective lifetime (τ*) in undoped a-Si:H films have been measured by the Flying Spot Technique (FST). This technique consists in measuring the decay range of charges in Schottky barriers and the potential induced by a laser beam with a constant motion rate. The data show that the FST measurements are quite suitable to determine separately the effective diffusion length and the effective lifetime of the carriers, taking into account the surface effect. The results also indicate that the photosensitivity is not the best parameter to characterize film quality. Indeed, films with high photosensitivity can present a poor lifetime and diffusion length that make them unsuitable to be used in optoelectronic devices. The results obtained by FST have been correlated with the Density of States (DOS) inferred by the Space Charge Limited Current (SCLC) measurements performed in the temperature range of 300–430 K and by the Constant Photocurrent Method (CPM) in forward biased Schottky diodes at room temperature. The dependence of the DOS on temperature shows that the SCLC technique is clearly influenced by the thermally activated carriers.

scholarly journals Direct determination of the ambipolar diffusion length in strained InxGa1−xAs/InP quantum wells by cathodoluminescence

1993 ◽  
Vol 62 (19) ◽  
pp. 2411-2412 ◽  
Author(s):  
Robert B. Lee ◽  
Kerry J. Vahala ◽  
Chung‐En Zah ◽  
Rajaram Bhat
Keyword(s):  
Quantum Wells ◽  
Diffusion Length ◽  
Direct Determination ◽  
Ambipolar Diffusion

Hydrogenated Amorphous Silicon Speed Sensor Based on the Flying Spot Technique

1995 ◽  
Vol 377 ◽  
Author(s):  
M. Vieira ◽  
A. Fantoni ◽  
A. Maçarico ◽  
F. Soares ◽  
G. Evans ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Material Characterization ◽  
Diffusion Length ◽  
Hydrogenated Amorphous Silicon ◽  
Effective Lifetime ◽  
Object Position ◽  
The Past ◽  
Speed Sensor ◽  
Hydrogenated Amorphous ◽  
Flying Spot

ABSTRACTIn the past we have developed a transient technique, called the Flying Spot Technique (FST). FST allows, not only to infer the ambipolar diffusion length but also the effective lifetime of the photogenerated carriers once the light spot velocity and geometry of the structure were known.In this paper, we propose to apply this technique backwards in order to detect the path and velocity of an object that is moving in the direction of a light source. The light reflected back from the object is analyzed through a p.i.n structure being the transient transverse photovoltage dependent on the movement of the object (position and velocity). Assuming that the transport properties of the material and the geometry of the device are known and using a triangulation method we show that it is possible to map the movement of the object. Details concerning material characterization, simulation and device geometry are presented.

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