Crystal growth and characterization of Mg2Si for IR-detectors and thermoelectric applications

We have investigated the melt growth of Mg2Si crystal and its electrical and optical properties. Progress in Mg source purity and stoichiometric control during the growth enabled the development of a high purity Mg2Si crystal with low carrier density and a high stable Mg2Si with good doping controllability. The Mg2Si crystal grown by the pressure controlled Bridgman method using 5N purity or 6N purity of Mg source and purified PG crucible showed low electron density (∼1015 cm−3) and high electron mobility (485 cm2 V−1 s−1 at 300 K and 21900 cm2 V−1 s−1 at 40 K). Silver doping in the high purity crystals performed the low-hole density of p-type Mg2Si (∼3 × 1016 cm−3). Ionization energy of residual Al donor in the high purity crystal and Ag acceptor in the Ag doped crystals was determined as 8–9 meV and 26 meV, respectively. Indirect band gap energy Eg of approximately 0.61 eV at 300 K and 0.69 eV at 4 K were estimated by the optical transmission measurements on the high purity crystals. It is also found that the Sb-doped melt grown crystal had good power factor around room temperature (26 µW cm−1 K−2 at 270 K).