ZnO is a direct wide-band gap semiconductor with WZ crystal structure.Due to the low growth temperature and high exciton binding energy(60 meV)at room temperature

it is an ideal semiconductor material with blue light enission.As the development of semiconductor growth technology

high quality ZnO can be obtained

and the research in ZnO attracts much more attention again.In this paper

high quality ZnO thin films on sapphire substrate have been obtained by MOCVD system designed by ourselves.At the same time

the properties of annealed and doped ZnO films have been investigated in details

and good results have been achieved.According to the principle of MOCVD and in order to solve the problem in ZnO growth process

new-type plasma enhanced MOCVD system has been designed and fabricated.The precursors(DEZn and O

2

)has been introduced into the reactor by two gas lines

respectively.And the precursors arrive to the surface of sapphire substrate by two separated special injectors.The substrate holder can be rotated at high speed and is uniformly heated by a special resistive heater.In order to balance the thermal flow

N

2

is introduced into the reactor uniformly from the upside of the reactor.All above design can reduced the pre-reaction of DEZn and O

2

during the ZnO growth and uniform ZnO films may be grown by this MOCVD system.Furthermore

the plasma generator has been added to the MOCVD system in order to improve doping efficiency during ZnO growth process and to obtain high resistivity or p-type ZnO films.High quality ZnO films have been firsly grown on sapphire substrate in optimized growth condition by MOCVD.At the same time

the doping properties of NH

3

in ZnO film grown on R-plane sapphire were also firstly investigated.After optimized the growth conditions

only

<

110

>

oriented ZnO film were obtained under NH

3

flux of 80 sccm.Furthermore

the FWHM of ZnO(110)XRD peak is only 0.50°.The AFM images sbow that the surface of the film is the most smooth.Up or low the flux

the surface will become rough and the crystal quality also decreases.The Hall measurements show that the sample grown under NH

3

flux Of 50 sccm is low p-type conductor with the resisitivity 102Ω·cm

hole concentration+1.69×10

16

cm

-3

and mobility 3.6cm

2

·V

-1

·s

-1

.The XPS spectra show that nitrogen and zinc atom forms N-Zn bond under NH

3

flux of 50 sccm.As the flux increase

some hydrogen atom is introduced into ZnO film

and the conductivity change into n-type.The sample resistivity is up to 10

8

Ω·cm under NH

3

flux of 80 sccm.