Semiconductors Investigated by Time Resolved Spectroscopy Using Femtosecond and Picosecond Laser Technology.
Final rept. 1 Dec 84-30 Nov 85,
CITY COLL NEW YORK ULTRAFAST SPECTROSCOPY AND LASER LAB
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Four major accomplishments have been achieved to help further the development of faster photonic and electronic devices. 1. We have shown theoretically and experimentally how one can determine accurately one of the most important parameters in microstructures the bandgap discontinuity in valence and conduction bands at the heterojunction from the photoluminescence measurements for ultrathin wells in the range of 15 to 80 A for GaAsAlGaAs and GaInAsAlInAs structures. 2. A model was developed using the electron degeneracy to describe the much slower carrier - optical phonon loss relaxation rate measurements in 2D as compared to 3D. 3. The valence and conduction band deformation potentials were separately determined for the first time in semi magnetic semiconductor alloys of Cd1-xMnxSe from the shift in photoluminescence spectra versus x. The valence band deformation potential of wurtzite crystals is much larger compared to the one in zinc blende. This technique measures separately the values of valence and conduction band deformation potential instead of the difference between them. 4. The direct picosecond spin dephasing time and degree of spin alignment of photoexcited electrons in semi-magnetic semiconductor alloys of Cd1-xMnxSe was measured. The fast dephasing times arise from the spin exchange between free carriers and the localized Mn ions.
- Electrical and Electronic Equipment
- Solid State Physics