Mechanism and Applications of large and persistent photoconductivity in cadmium sulfide

Photoconductivity is the phenomenon where electrical conductivity changes as a result of photoexcitation of new charge carriers. In some semiconductors, photoconductivity is accompanied with enormous conductivity change and long decay time after photoexcitation is ceased. This effect is called large and persistent photoconductivity (LPPC). LPPC is due to the trapping of photo-generated minority carriers at crystal defects. Theory has suggested that anion vacancies in II-VI semiconductors are responsible for LPPC due to negative-U behavior, whereby two minority carriers become kinetically trapped by lattice relaxation following photo-excitation. By performing a detailed analysis of photoconductivity in CdS, we provide experimental support for this negative-U model. We also show that, by controlling sulfur deficiency in CdS, we can vary the photoconductivity of CdS films over nine orders of magnitude, and vary the LPPC characteristic decay time from seconds to 10⁴ seconds.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Mechanical Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2020

Author dc:creator

• Yin, Han,Ph.D.Massachusetts Institute of Technology.

Advisor dc:contributor.advisor

• Rafael Jaramillo.

• Mechanical Engineering.

Statement dc:rights

• MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/127735

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/127735