ELECTROOPTICAL MEASUREMENTS IN A SEMICONDUCTOR - THE CASE OF CDLN2TE4

The precautions which have to be taken in measuring electro-optical co efficients of some semiconductors are emphasized. It is shown that cla ssical measurements using a lock-in amplifier may lead to erroneous re sults if ohmic contacts are not obtained. In presence of Schottky cont acts, electro-optical coefficients may still be determined provided th at measurements are performed in dc fields and that also an adequate t heoretical model based on a linear distribution of the electric field at the interfaces is used. The model is tested with the electro-optica l semiconductor CdIn2Te4. Electrical properties of contacts were inves tigated by using I-V and C-V measurements. Then electro-optical measur ements in ac and dc fields are compared. Special attention is paid to dc measurements, and results are in very good agreement with those pre dicted by the model. Finally, a value of the electro-optical coefficie nt r41 of CdIn2Te4 close to 3 pm V-1, and not 50 pm V-1 as already ann ounced, is found.