Gallium oxide(Ga

2

O

3

)

a wide direct-gap semiconductor(

E

g

≈4.9 eV)

has recently attracted interests as a new material for a gas sensor

transparent conductor

luminescent phosphors

solar cells

electronic and optoeclectonic applications.For Ga

2

O

3

films growth

numerous deposition techniques including sputtering

electron-beam evaporation

molecular beam epitaxy(MBE)

pulse-laser deposition(PLD)

and metal organic chemical vapor deposition(MOCVD)have been employed.Among these techniques

MOCVD has many advantages for volume production and it has been proved to be excellent growth technique for Ⅲ-Ⅴs especially for the nitrides.Ga

2

O

3

films used in this study were grown by a home-built vertical atmospheric pressure MOCVD system.Deionized water and trimethylgallium(TMGa)were used as the O and Ga sources

respectively

using nitrogen as the carrier gas.Typical growth conditions were as follows:chamber pressure was 103.3 kPa.The thickness of buffer layer is about 15 nm

growth temperature was 500℃

epilayer growth temperature was 700℃

and a total carrier gas flow rate was about 15000 sccm.The thickness of the Ga

2

O

3

layer was about 2 μm.Ga

2

O

3

epilayer characteristics were investigated by AFM

X-ray diffraction(XRD)and secondary ion mass spectroscopy(SIMS).The results of AFM indicated the Ga

2

O

3

films grew up with columniation shape and the structure was relatively compact.The root mean square(RMS)roughness as determined by AFM(30 μm×30 μm)of the film surface was about 40 nm.The Ga

2

O

3

grain size was about 30～40 nm determined by AFM.X-ray diffraction spectrum showed that the FWHM of(

1

02)diffraction peak was 0.25°

which indicated the good quality of βGa

2

O

3

film.The Ga

2

O

3

grain size was calculated about 32 nm by Scherrer's formula

which was consistent with the result of AFM.The results of SIMS showed that the Ga

2

O

3

epitaxial films had good purity.