Significance of Charged Defects in Understanding the Light-Induced Degradation of Hydrogenated Amorphous Silicon-Germanium Alloys

Research output: Contribution to conferencePaper

Abstract

We have characterized the defect state structure in a series of device quality glow discharge intrinsic, n-type doped, and p-type doped a-Si,Ge:H alloys with Ge content ranging from 20 at. percent to 35 at. percent. Our experimental methods include capacitance profiling, transient junction photocurrent and photocapacitance measurements. These methods have allowed us to identify one type ofthermally induced defect transition plus two types of optical transitions from deep defects. Our results indicate that these transitions must involve at least two distinct defect sub-bands. Comparison of the magnitudes of these sub-bands for the intrinsic, n-type, and p-type alloys has allowed us to confirm that one of the optical transition belongs to D+ defect sub-band. All the optically andthermally induced bands of defect transitions are present with similar magnitudes for the most intrinsic a-Si,Ge:H alloys, which implies that charged defects play a significant role in glow discharge a-Si,Ge:H alloys. We then examined the changes in these defect densities, along with the changes in the hole mobility-lifetime products, that result from prolonged light exposure. By comparing theannealed state and light soaked state of each sample, we have been able to correlate the relative changes of the identified defect sub-band with the measured hole mobility-lifetime products. These data indicate that charged defects probably play a dominant role in determining the degradation of these a-Si,Ge:H alloys in device applications.
Original languageAmerican English
Pages55-60
Number of pages6
StatePublished - 1997
EventAmorphous and Microcrystalline Silicon Technology 1997: Materials Research Society Symposium - San Francisco, California
Duration: 31 Mar 19974 Apr 1997

Conference

ConferenceAmorphous and Microcrystalline Silicon Technology 1997: Materials Research Society Symposium
CitySan Francisco, California
Period31/03/974/04/97

Bibliographical note

Work performed by University of Oregon, Eugene, Oregon and United Solar Systems Corp., Troy, Michigan

NREL Publication Number

  • NREL/CP-520-24541

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