New Bragg Reflector Enhanced UV Solar-Blind Photovoltaic Detector on Si

摘要

The objective of this project is to study MBE growth of PbSrSe with different Sr composition and the potential for detector applications. The PbSrSe material system ranges from UV wide bandgap semiconductor SrSe (3.8e eV) to mid-IR narrow gap semiconductor PbSe (0.26 eV). Therefore it is a very interesting material system to study. During this project, MBE-grown PbSrSe epitaxial layers with Sr composition ranging from 1 to 0 have been successfully demonstrated on Si and BaF2 substrate. The bandgap energies as well as the refractive indices were determined by optical transmission measurement. A distinct bandgap inversion from the direct to the indirect transition is observed for the first time at x (caret)0.20 as the Sr composition increases. In situ reflection high energy electron diffraction (RHEED), x-ray diffraction, and optical transmission are used to characterize the epi-layers and show that the material quality is reasonably high. However, doping - especially p-type doping - for wide gap SrSe is difficult. There is no doping problem for narrow gap small Sr composition PbSrSe materials. A new concept of growing PbSe-based quantum well materials on 110 orientation was also proposed. Preliminary MBE growth was successful. Future work will be focused on new detector structures on 110 orientation.