Disorder-induced enhancement of indirect absorption in a GeSn photodetector grown by molecular beam epitaxy
Abstract
We report an investigation on the absorption mechanism of a GeSn photodetector with 2.4% Sn composition in the active region. Responsivity is measured and absorption coefficient is calculated. Square root of absorption coefficient linearly depends on photon energy indicating an indirect transition. However, the absorption coefficient is found to be at least one order of magnitude higher than that of most other indirect materials, suggesting that the indirect optical absorption transition cannot be assisted only by phonon. Our analysis of absorption measurements by other groups on the same material system showed the values of absorption coefficient on the same order of magnitude. Our study reveals that the strong enhancement of absorption for the indirect optical transition is the result of alloy disorder from the incorporation of the much larger Sn atoms into the Ge lattice that are randomly distributed.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 09, 2016
- Source ID
- 10.1063/1.4949533
Entities
People
- ChuanâChieh Chang
- Greg Sun
- H. H. Cheng
- Huanan Li
- Richard Soref
Organizations
- Air Force Office of Scientific Research
- National Science and Technology Council
- National Taiwan University
- United States Army
- University of Massachusetts Boston