Properties of Pb1−<i>x</i>Eu<i>x</i>Te films prepared by hot-wall epitaxy

Abstract

Pb1−xEuxTe films were prepared by hot-wall epitaxy, evaporating PbTe, Eu, and Te from the same quartz-tube furnace onto BaF2 (111) substrates. Good crystalline films were obtained by preparing the films in excess Te vapor. Dependence of the energy band gaps and lattice constants of the Pb1−x EuxTe films on the EuTe content was measured through the optical absorption, x-ray diffraction, and x-ray microanalysis. Temperature dependence of the energy band gap was also measured. Single-phase films with Eg ≤0.83 eV and x≤0.26 were obtained. Derivatives of the band gap with respect to the EuTe content x(dEg/dx) were 3.5 eV at 300 K and 4.5 eV at 77 K up to x=0.06, and the value decreased for x&amp;gt;0.06. Electrical properties of the Pb1−xEuxTe films were also measured. Bi and Tl were used as donor and acceptor impurities, respectively. High carrier concentration (n, p≥1018 cm−3) and low resistivity films were obtained up to x=0.06 (Eg =0.55 eV).