Charles University > Faculty of Mathematics and Physics > Institute of Physics

Division of Optoelectronics and Magnetooptics

http://semiconductors.mff.cuni.cz

The work in the Division of Optoelectronics and Magnetooptics is focused on the research of the material CdTe and (CdZn)Te. The complete galvanomagnetic properties of the solid state in the whole range of the stability over 600C have been measured. We studied also kinetics and diffusion processes. We reached to define diffusion constant, prepare contacts for measurments in range 0–500C. This temperature range seems to be key player for futher understanding of the properties of point defects, mainly for their interaction and creation of complexes. The first outcome of these measurments is the mobility of holes, which for the first time was measured in this temperature range. At same time the research of liquid CdTe was done. We measured the conducivity of CdTe at defined pressure. We managed to find relation between undercooling of liquid and pressure of Cd, with growing pressure of Cd undercooling is decreasing. The practical aim of these measurments is to gain the information for optimalization of the growth technology, preparation of superior high-resistivity detectors and substrates (CdZn)Te.

PPT presentaion of results: here , here and also here .

Newly achieved results of photoluminescenece CdTe crystal mapping at liquid helium temperatures available here .

The research in this field 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)