Zn is one of the accepor dopants for getting the hightest efficient radiate recombination centers in GaN

[1]

. It is reported that the different Zn concentration in Zn-doped GaN can provide emission colors of blue

green

yellow and red

[2-4]

.So the problem non-uniformity of Zn concentration in the layer if GaN by VPE must be solved. Monemar et al

[4]

. have showed that Zn concentration was related to the position of substrate in a reactor chamber. High ohmic resistance Zn-doped GaN layer was not at the front of reaction zone but at some distance of the reaction zone. A typical variation in resistivity was a factor of 40 when the substrats were arranged in a region of 15 mm along the reaction zone. This behavior can partly be explained by the vari-arion of

N

-vacancy concentration in this growth direction. We have investigated a lot of samples of Zn-doped GaN. It was observed that the concentration of Zn was non-uniform in the VPE layers of GaN.Variant position for obtaining ohmic Zn doped GaN was different even on the same sample surface

resulting in different emission spectrum.This phenomena may connect with defects of grown GaN such as helical dislocation different morphology and growing pits on the GaN epitaxy layer surface.