Semiconducting Mg2Si is known as a thermoelectric material and recently attracts increasing attention as a Si-ased, low-cost and environmental friendly material for an infrared (IR) sensor. With the aim of producing cost-fective Mg2Si single crystal substrates for the IR sensor, we have investigated single crystal growth of Mg2Si using the vertical Bridgman (VB) and micro-pulling-down (mu-PD) methods in open-system. Since the evaporation of Mg was not suppressed during the mu-PD, the composition of the Mg2Si single crystal grown by this method was not stoichiometric. On the other hand, single crystalline Mg2Si was produced by the VB method using the Si-treated inner carbon seat and BN-coated carbon crucible. The Mg2Si crystals with a diameter of 30 mm were grown at a growth rate of 0.5 mm/min and a temperature gradient of 5 degrees C/cm. The electron density and mobility of the crystal so obtained were 1.8x10(17) cm(-3) and 283 cm(2)V(-1)s(-1) at 300 K, respectively. The high electron density was due to contamination from the impurities presented in the crucible.