ZnO is a wide band gap semiconductor with 3.36eV at room temperature. It has been studied for decades for its many applications

such as surface acoustic waveguide

transparent electrodes for some solar cells and buffer layer for epitaxy of GaN. In recent years

ZnO film attracted more attention due to its applications in photoelectric materials. It has been found to be possibly used in ultraviolet laser devices due to its ability to emit stimu lated ultraviolet photons. The shorter wavelength laser devices can provide many new applications. In order to fabricate photo electronic diodes

research on the electrical properties is now urgently needed. Using the method of Hall effect experiment

we can get some information on the semiconductor

such as the carrier concentration

conductance and transfer rate. For the sample of films

Van der Pauw method is very useful. It can be applied to measure the samples with anomaly geometry. But there were few detailed reports on the measu ring of ZnO films by using this method. Using Van der Pauw method to measure the ZnO films

the first problem is to prepare electrode

which is ohmic contact with ZnO films. Al is mostly used as ohmic electrode

but we found another Ag alloy material with lower contact resistance

which is better as ohmic electrode than Al. Second

it is stable at low temperature(77K)

but Al is not. The last

the Ag alloy electrode is much easier to prepare. Using the Ag alloy as the ohmic contact

we get the carrier concentration of the sputtered ZnO prepared on glass substrate at room temperature to be 1.04×10

17

cm

-3

; the resistivity of 2.25Ω·cm and the transfer rate of 26.7cm

2

/V·s. We also get the temperature dependence of DC resistivity of the sputtered ZnO films. At high temperature (

>

280K)

σ formally obeys the following formula: σ=σ

0

exp(-

E

a

/

KT

) where σ

0

is a pre exponential factor

E

a

the activation energy for band conduction

and K the Boltzmanm constant. And we find the activation energy of sputtered ZnO is 0.035eV. At lower temperature(77～280K)

the dependence is different from the normal semiconductor. It may be caused by the drift of the impurity ions in grain boundary barrier.