Annealing in vacuum will lead to out diffusion of the constituents of the material in the surrounding vacuum. If there is a nitrogen atmosphere the nitrogen present in the annealed material will not escape out of the material. If they escape they will be be substituted by from the nitrogen environment. So, in order to preserve the the nitrogen content at the nonmetallic area of the device. This may be the main cause of annealing under nitrogen.
Annealing in vacuum will lead to out diffusion of the constituents of the material in the surrounding vacuum. If there is a nitrogen atmosphere the nitrogen present in the annealed material will not escape out of the material. If they escape they will be be substituted by from the nitrogen environment. So, in order to preserve the the nitrogen content at the nonmetallic area of the device. This may be the main cause of annealing under nitrogen.
Thank you Prof. Abdelhalim Zekry . Actually I am working on MgZnO/ZnO based HFET. It is oxide material after this I saw in literature every one uses a nitrogen environment.