GaN has a direct bandgap of 3.5eV and thus gives luminescence over the entire visible spectrum.Zn dopants are disposed for a broad blue luminscence bands in GaN

but the nature of deep centres responsible for their bands is not well established

nor is the radiative mechanism involved.A detailed study of 2.89eV photoluminescence(2K)transient in GaN:Zn at different time range was given.The lifetime turns out to be 300ns at 2K(Fig.3)and slightly faster at 77K

in accordance with the result obtained from time-resolved spectroscopy(Fig.4).However

the decay-curve of long-period(50 μs)is nonexponential

fitting the Becqueral type of relation.Its kinetics appears to be more complicated.The luminescence intensity decay obeys the law of

I

=

I

c

/(1+

bt

)

a

.We have found

a

=1.8 from the analysis of experiment curve(Fig.5).This demonstrates that the luminescence should be interpreted as a bimolecular mechanism rather than monomolecular.Its decay corresponds to a hyperbolic curve approximately.Temperature dependence of 2.89eV luminescence has been observed.The rapid decrease of 2.89eV luminescence efficiency can be seen above 160K.It is responsible for nonradiative transitions full sense.The assumption is consistent with those obtained by other authors.These values of activation energy for the nonradiative recombination have a range of 0.18-0.49eV.In conclusion

it is clear that the transient process of deep centre Zn in GaN is not so simple

Zn not only forms a deep acceptor

but causes non-radiative recombination or other traps probably.Our results show that Zn is complex centre.The nature of 2.89eV blue luminescence is interpreted as due to the radiative recombination between photo-excited electrons in conduction band and holes bound at the ZnGa acceptor taking into account traps perturbation.