A tunneling spectroscopy study of the temperature dependence of the forbidden band in Bi2Te3 and Sb2Te3

Tunneling measurements of dI/dV, d I-2/dV (2), and d I-3/dV (3) were performed along the C-3 axis (normally to layers) for Bi2Te3 and Sb2Te3 layered semiconductors in the temperature range 4.2 < T < 295 K. Temperature dependences of the forbidden band energy E-g were obtained. The forbidden band energy in Bi2Te3 was 0.20 eV at room temperature and increased to 0.24 eV at T = 4.2 K. The E-g value for Sb2Te3 was 0.25 eV at 295 K and 0.26 eV at 4.2 K. The distance between the top of the higher valence band of light holes and the top of the valence band of heavy holes situated lower was found to be DeltaE(V) approximate to 19 meV in Bi2Te3; this distance was independent of temperature. The conduction bands of Bi2Te3 and Sb2Te3 each contain two extrema with distances between them of DeltaE(c) approximate to 25 and 30 meV, respectively. (C) 2003 MAIK Nauka/Interperiodica.