Temperature dependence of the fundamental absorption edge of HgBr2 and HgBrI single crystals

Mercuric bromide (HgBr2) and mercuric bromide iodide (HgBrI) are layered se miconducting compounds exhibiting promising features and can be considered as candidates for nuclear radiation detector applications that operate at r oom temperature. In the present work, the optical transmission spectra of H gBr2 and HgBrI single crystals were measured in the fundamental energy gap region, in the 11-310 K temperature range, and the absorption spectra were obtained. The absorption coefficient exhibited exponential behavior followi ng Urbach's rule, for both compounds. The values of the energy gap at sever al temperatures as well as the temperature dependence of these compounds we re determined, and a comparison was made with the corresponding features of HgI2. (C) 1999 Elsevier Science Ltd.