Division of Optoelectronics and Magnetooptics

http://semiconductors.mff.cuni.cz

The division of Optoelectronics and Magnetooptics is focused on the complex research of the high resistive seniconductors (CdTe/(CdZn)Te, GaAs, SiC, TlBr, Perovskites and others). The galvanomagnetic properties of the solid states in the whole range of their stability over 77K-1200K have been measured. This temperature range seems to be the key region for the futher understanding of the properties of point defects, mainly for their interaction and creation of complexes. We studied also charge transport kinetics and diffusion processes. The first outcome of these measurements are the carrier mobility and lifetime and diffusion coefficient. We are also able to measure the conducivity of semiconductors at defined pressure to find relation between undercooling of liquid and partial pressure of each components. The practical aim of these measurments is to gain the information for the optimalization of the growth technology and preparation of the enhanced quality of radiation detectors.

For detail characterization of transport properties of semiconductors we have used the ToF method using Laser-induced transient current technique (L-TCT). We are able to evaluate drift mobility of charge carriers and their lifetime, internal electric field profile and dynamics of the spase charge formation. We are also focusing on the deep and shallow defect levels characterization.

The another research is aimed to the optical properties of double quantum wells in magnetic and electric fields.

Why double quantum wells?

Double quantum well (DQW) represents a structure that allows of the study of basic quantum phenomena in the transition from 2D to 3D systems. In particular, a lot of attention has been payed to excitons, i.e. to the coupled electron-hole excitations. The DQW enables the formation of a spatially indirect exciton (IX) when an electron and a hole are located in opposite wells, see picture bellow.

The spatial separation leads to their very long lifetimes, usually three orders of magnitude longer than for intrawell (direct) excitons (DX). Another special feature of excitons is their bosonic character. Thus, the gas of free excitons behaves according to the Bose-Einstein statistics and in case of the long living IXs a transition to a Bose-Einstein condensate is predicted at low temperatures. (the best link available in this field is Homepage of Leonid V. Butov)