Semiconductor band-gap energy can be measured by using photoreflectance (PR) spectroscopy. It used a pump-beam and a probe-beam and measure modulated reflectance (DR) of the probe-beam by chopping on and off the pump-beam. The photon-energy of the pump-beam has to be greater than the band-gap energy of the sample so that electron-hole pair can be produced in the sample. The electron-hole pairs are separated by built-in electric field (Fbi) of the sample and thus reduce strength of Fbi. In this work the Hg lamp was used for the pump beam to observe E_1 and E_1+∆E_1 transitions of GaAs, and its photon energy is greater than E_1 and E_1+∆E_1 bandgaps. We also used the purple, green and red laser to observe GaAs, and their photon energy are greater than E_0 but smaller than E_1gaps. Finally, we will compare the amplitude of the PR spectra with the strength of the Fbi reduced by the pump-beam.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0719112-165625 |
| Date | 19 July 2012 |
| Creators | Chang, Chih-Chong |
| Contributors | Chi-Huang Lin, Dong-Po Wang, Bae-heng Tseng |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0719112-165625 |
| Rights | user_define, Copyright information available at source archive |
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