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

Abstract

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).

Control of the Thermoelectric Properties of Mg2Sn Single Crystals via Point-Defect Engineering

“…As shown in Fig. 5d, μ increases from 89.9(8) cm 3 /Vs to 132.6(28) cm 3 /Vs, which is inversely proportional to n. Such a relation between n and μ has also been reported for an Mg 2 Si single crystal 46 .…”

Infiltration of Cellular Silicon by Molten Magnesium Alloys

“…In the system Mg–Si (Figure ), the diffusion layer is formed in a homogenous manner, but with noticeable variations in thickness. Furthermore, this layer shows continuously distributed cracks arising from stress–strain concentration around Mg 2 Si cleaving it at {111} planes . Due to the lattice mismatch of Si and Mg 2 Si, the growth of the intermetallic diffusion layer provokes the development of dislocations .…”

Oxidation resistance of impurity doped Mg2Si grown from the melt

“…Hence, practical application of Mg2Si is expected in the intermediate temperature range because of its high thermoelectric properties [2]. A number of donor impurities such as Bi, Sb, As, P and Al are investigated to optimize the electron concentration for obtaining the optimal ZT and thermoelectric properties in Mg2Si [3][4][5][6][7][8][9][10]. On the other hand, durability of the thermoelectric material is a major important issue as similar to the ZT for practical applications.…”