We investigated the temperature and bias voltage dependencies of spin injection signals for Co₂FeAl_0.5Si_0.5 (CFAS)/n-GaAs schottky tunnel junction. Clear voltage change was observed at 10 K for the junction by 3 Terminal Hanle measurements. The maximum voltage change, ΔV_MAX, was decreased with increasing temperature and observed up to 100 K. The estimated spin relaxation time, τ, was 290 ps at 10 K and was also decreased with increasing temperature. In addition, temperature dependency of τ was lower than that of ΔV_MAX. The ΔV_MAX was increased with increasing bias voltage, and the sign of ΔV_MAX was reversed by opposite bias voltage direction. Moreover, bias dependency of ΔV_MAX became insensitive with increasing temperature.