Raman studies of heavily carbon doped GaAs
Abstract
Raman spectroscopy is used to study GaAs heavily doped with carbon. Hole concentrations in these samples range from 2.3 × 10^19 to 1 × 10^20 cm-3. Three main Raman features are investigated: the longitudinal-optic (LO) phonon mode, the substitutional carbon-at-arsenic local-vibrational mode, and the coupled plasmon-LO phonon present due to the interaction between the LO phonon and the free carriers. Only one allowed phonon-like coupled mode is observed due to the large plasmon damping and high effective carrier masses in this system. The coupled mode is seen to systematically red shift as carrier concentration increases. This behavior is described by a model which includes the effects of high hole concentrations on the dielectric function and an additional shift in the optic phonon we attribute to carbon size effect. The local vibrational mode intensity is found to be directly proportional to the carrier concentration p. Interestingly, the local mode intensity shows good correlation with that of the coupled plasmon-phonon mode as a function of p. The intensity of the coupled plasmon-LO phonon mode to that of the LO phonon is determined to be a good indicator of the carrier concentration.
- Publication:
-
APS Texas Sections Fall Meeting Abstracts
- Pub Date:
- October 1998
- Bibcode:
- 1998APS..TSF..CB06S