High Electric Field Electron Transport in Semiconductors Studied by Raman Spectroscopy
Abstract
High electric field electron transport in GaAs and rm Al_{x}Ga_ {1-x}As (x = 0.3) p-i-n structures has been studied by using electronic Raman scattering from spin density fluctuations. The transient transport property of velocity overshoot was investigated on the picosecond and subpicosecond time scales. For GaAs, picosecond transient Raman scattering experiments for electric strengths up to 35 kV/cm were performed. The effects of photoexcitation energy and carrier concentration on the electron distribution functions and drift velocity were investigated. Electron distribution functions and electron drift velocities were directly determined from the Raman scattering cross section. Depending upon the photoexcited electron density, electron distribution functions were seen to range from being highly nonequilibrium to being in quasi-equilibrium. For AlGaAs, picosecond transient Raman scattering experiments were performed for a photoexcitation energy below the E _{o} + Delta band gap, which gave rise to highly nonequilibrium electron distributions. Subpicosecond Raman scattering experiments were performed on the GaAs p-i-n structure. Highly nonequilibrium electron distributions were observed on this time scale, and the experimentally measured drift velocities indicated that, when compared with those determined in the picosecond studies, the electrons were in the velocity overshoot transport regime. The effect of a high electric field on the nonequilibrium LO phonons was also investigated. The carrier dynamics were also studied by using time-resolved Raman spectroscopy from the spin density fluctuations.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1995
- Bibcode:
- 1995PhDT.......126G
- Keywords:
-
- GALLIUM ARSENIDE;
- ALUMINUM GALLIUM ARSENIDE;
- Physics: Condensed Matter