Electro-absorption sampling at terahertz frequencies in III-V semiconductors

Abstract

We review recent advances in the development of a new sampling technique for ultra high-speed electrical signals. It is based on the electro-absorption phenomena in semiconductors (Franz-Keldysh effect). We demonstrate that it is usable up to the terahertz range. The theory is exposed and we show two practical set-ups. The first uses the semiconductor substrate (internal sampling). The second uses a small semiconductor probe bonded on the circuit (external sampling). In this last case, the theoretical temporal resolution is about 200 fs. In practice, we measure a risetime of about 500 fs with 60 dB of dynamic range.

The electric‐field effect on the exciton photoconductivity and Urbach tail in GaSe crystals

“…Hence, we may try to explain the observed shift in the exciton photoconductivity peak of GaSe crystals using the Franz-Keldysh effect that has been used for crystals having Urbach tails in their absorption spectra. Theoretically, this shift is given as [7,8,[24][25][26]:…”