In resent years there has been great interest in combining ferroelectric thin films with semiconductor materials.If integration between ferroelectric materials and semiconductor materials can be achieved directly in epitaxial growth

it would open possibilities to explore new applications and new physical phenomena. This paper reports the molecular beam epitaxy(MBE)growth of the GaAs films on the SrTiO

3

substrates with different orientations ((100)

(110) and (111)).Micro-Raman and photoluminescence(PL) measurements are used to detect the optical properties of these new kinds of heterojunction structures.Two Raman peaks near to 269 and 292cm

-1

have been observed which corresponding to the TO and LO phonons of the GaAs single crystal.These show that the GaAs films are well crystallized.Micro Raman studies also show that the rate of the intensity of LO and TO peaks of the GaAs films are different for the different orientations of SrTiO

3

.It indicates that the orientations of the GaAs films are different. PL studies show the intensity of the PL peak of GaAs on (100) and (111) SrTiO

3

are quite weak

and large blue shifts (more than 10meV) are observed.These are caused by the large difference of surface lattice periodicity and crystal structure between GaAs and SrTiO

3

.The intensity and the position of the PL peak of GaAs film on (110) SrTiO

3

are similar to that of single crystal film.These results show the optical quality of the GaAs film on (110) SrTiO

3

is much better and can compared with that of single crystal film.