Research Topics
Ultrafast laser spectroscopy
Time-resolved photoluminescence measurement (TRPL)

CdSe photoluminescence
Terahertz spectroscopy of semiconductors and nanostructures
      Frequency-dependent complex THz conductivities and dielectric responses of the InN epilayer and vertically-aligned InN nanorods measured by THz time-domain spectroscopy (THz-TDS). Using the Drude model for carrier conduction, the key parameters that determine the free carrier dynamics of the InN film are extracted. Those parameters for the InN nanorods, however, are best fitted by applying Drude-Smith model, which includes the scattering effect of electrons along the boundary of nanorods.

Terahertz emission and emission mechanism

Photo-Dember effect
¨Semiconductors with small bandgap, such as InAs (0.36eV) and InSb(0.23eV)
¨The absorption depth is very small (~100nm)
¨excess energy of photoexcited carriers is very large¨
Band bending is not obvious small surface depletion field

Surface depletion field

Semiconductors with wide bandgap, such as GaAs (1.43 eV) and InP (1.34 eV)
The surface states exist in the forbidden gaps within the bandgap and Fermi-level pinning occurs
¨The electrons and holes are accelerated in opposite direction by the built-in field to drive a surge current.

Material nonlinear optics measurement (Z-scan)
Carrier dynamics- Pump probe experiment

 Terahertz interferometer

Since 2008/3/27
Copy Right (c) 2008 Ultrafast Semiconductor Photonics Lab