Exploration of Defect Relaxation Dynamics in Hydrogenated Amorphous Silicon using Temperature Switching Experiments

1994 ◽  
Vol 336 ◽  
Author(s):  
Adam Gardner ◽  
J. David Cohen
Keyword(s):  
Density Of States ◽  
Thermal Emission ◽  
Hydrogenated Amorphous Silicon ◽  
Relaxation Processes ◽  
Relaxation Dynamics ◽  
Temperature Step ◽  
Thermally Activated ◽  
Hydrogenated Amorphous ◽  
Defect Relaxation ◽  
Transient Measurements

ABSTRACTWe have carried out a series of charge transient measurements on a-Si:H in which we insert a double temperature step during the period when electrons are being emitted from deep defects. The behavior of this emitted defect charge is completely inconsistent with any density of states that remains static during the emission; that is, defect relaxation must be invoked. Such measurements allow us to separate the temperature dependence of relaxation from that of thermal emission. In particular, we demonstrate that the emission itself exhibits thermally activated behavior in spite of the ongoing relaxation processes.

Deep Defect Relaxation in Hydrogenated Amorphous Silicon: New Experimental Evidence and Implications

1998 ◽  
Vol 507 ◽  
Author(s):  
J. David Cohen ◽  
Fan Zhong ◽  
Daewon Kwon ◽  
C.-C. Chen
Keyword(s):  
Fermi Level ◽  
Emission Rate ◽  
Thermal Emission ◽  
Hydrogenated Amorphous Silicon ◽  
Depletion Region ◽  
Time Resolved ◽  
Apparent Shift ◽  
Hydrogenated Amorphous ◽  
Defect Relaxation ◽  
Thermal Emission Rate

ABSTRACTWe review modulated photocurrent experiments which indicate that thermal emission rate for Do defects in intrinsic samples varies in response to changes in the Fermi-level or quasi-Fermi position. This apparent shift in energy threshold is confirmed using time resolved sub-band-gap spectroscopy. We also demonstrate that such a variation of emission rate with changes in the Fermi-level position, if present within the depletion region near a barrier junction, is consistent with the details of the temperature dependence of the junction capacitance in intrinsic samples.

Probing the Densities of Gap States in Intrinsic a-Si:H Using Space Charge Limited Currents of Electrons and Holes

1990 ◽  
Vol 192 ◽  
Author(s):  
Robin M. Dawson ◽  
J. H. Smith ◽  
C. R. Wronski
Keyword(s):  
Space Charge ◽  
Density Of States ◽  
Carrier Transport ◽  
Hydrogenated Amorphous Silicon ◽  
Wide Range ◽  
Self Consistent ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Space Charge Limited Currents ◽  
Space Charge Limited

ABSTRACTSpace charge limited currents of holes in intrinsic hydrogenated amorphous silicon (a-Si:H) have been obtained using novel p+-intrinsic-p+ (p-i-p) structures. The presence of these hole space charge limited currents is verified from their temperature dependence and their dependence on a wide range of intrinsic layer thickness. The carrier transport and space charge limited currents in the p-i-p structures are compared with those of n-i-n structures and the results are discussed in terms of a self consistent density of states in the gap.

Effect of Contacts on Capacitance Transient Measurements in N-Type Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
W. B. Jackson ◽  
N. M. Johnson ◽  
J. Walker
Keyword(s):  
Amorphous Silicon ◽  
Pulse Duration ◽  
Ohmic Contacts ◽  
Hydrogenated Amorphous Silicon ◽  
Charge Injection ◽  
Current Injection ◽  
Anomalous Dependence ◽  
Capacitance Transient ◽  
Hydrogenated Amorphous ◽  
Transient Measurements

ABSTRACTMeasurement of the dependence of emission capacitance transients on filling pulse duration has been extended to devices with Ohmic back contacts. Capacitance transients on devices possessing identical bulk 20-ppm P doped a-Si:H but either Ohmic contacts or blocking contacts were compared. The devices with blocking contacts completely reproduced in quantitative detail the previously observed anomalous dependence of capacitance transients on filling pulse duration. The diodes with Ohmic contacts showed no evidence of the anomalous filling pulse effect even for light-degraded, resistive samples. Current injection measurements show that blocking contacts delay the charge injection into the device by about 10–100 msec.

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