We report a study of the gate-induced spin precession in an In_0.53Ga_0.47 As two dimensional electron gas, using a Monte-Carlo transport model. The precession vector originates from the spin-orbit coupling existing at a III-V hetero-interface, usually denoted as Rashba interaction. Contrary to the case of a one dimensional electron gas, the precession vector is randomized by the scattering events, which leads to a non negligible loss of spin coherence for an initially spin-polarized electron population moving along a conduction channel. However, we show that by operating at the liquid nitrogen temperature, or by reducing the channel width to a value close to 0.1 micro-m, the gate-controlled spin-polarization remains high enough to enable the investigation of the physics of spin-related phenomena in a ferromagnet/semiconductor structure.