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Research Area - Nitrides

Time Resolved Optical Characterisation

The time resolved photoluminescence laboratory, TRPL, is located in the cleanroom area of the Physics House. It is well equipped with lasers, cryostats and several different optical detection systems.

The material characterisation are mainly focussed on to study different semiconductor crystals, either grown at the department or obtained from research collaborations. In a photoluminescence experiment lasers are used to excite carriers from the valence band over the bandgap to the conduction band. These excited carriers will recombine either directly or via defects in the material, and emitting a photon with a specific energy and wavelength.

The emitted emission from the sample, the photoluminescence, are collected and investigated with grating spectrometers to separate the different wavelenghts and photon energies.

Since many of the energy levels related to defects in a crystal are very small, the sample is usually cooled, sometimes to temperatures < 2 Kelvin to avoid temperature effects. This is done in He cryostates where liquid Helium or Nitrogen are used.

Specific for time resolved photoluminescence is that we are using pulsed laser to also observe the decay of the different emissions which gives further information about the recombination processes. To study the time behaviour of the emission we are using different detection systems with different time resolution and sensitivity.

The pulsed lasers also gives an increasing possibility to use non-linear crystals to increase the laser photon enrgy by doubling, tripling and quafrupling. Due to this our laboratory is specially well suited for time resolved spectroscopy of wide bandgap materials like SiC and Nitrides.

Responsible for this page: Fredrik Karlsson
Last updated: 03/20/13