Study On The Effects Of Electron Irradiation On GaN Heterostructure

The gallium nitride (GaN) grown on<0001> sapphire (Al2O3) substrate by metal organic chemical vapor deposition (MOCVD) technique were irradiated with2MeV-,1.7MeV-, and1MeV electron beam, respectively. The results of PL showed that the blue luminescence (BL) intensity would decrease after the2MeV,1×1015/cm2electron irradiation. However, no obvious appearance of Ga vacancies could be found in RBS/C curves. This was due to the native acceptors recombine with other point defects during the electron irradiation. The BL intensity rebounded once a large number of Ga vacancies were introduced by2MeV,5×10/cm2electron irradiation, this phenomenon indicated that the formation of BL is related with Ga vacancies. It was reasonable to believe that the1-charge state Ga vacancies act as the acceptors of BL. The as-grown and irradiated samples were measured by PL, the results of PL indiacated that the Ga vacancies (VGa) could recombine with ON during electron irradiation and form into VGa-ON complexes. The concentration of isolated ON decreased obviously after1.7MeV、1×1018/cm2electron irradiation.As-grown and irradiated samples were investigated by HRXRD. The HRXRD data presented that the high energy electron irradiation could result into the partial strain relaxation of GaN epitaxial layers. For the same energy electron irradiation, the visible strain relaxation was recognized for the GaN epitaxial layer by the high dose electron irradiation other than the low dose electron irradiation. EBSD was employed to characterize the misfit strain. The results of EBSD demonstrated that the Image Quality (IQ) of GaN epitaxial layer improved via the electron irradiation. It implied that the misfit strain of GaN epitaxial layer was released by electron irradiation. In accordance with the relaxation theory of elastic atom chain, we suggested that the most of interstitial atoms induced by electron irradiation migrated out the epitaxial layer and led to the strain relaxation.HRTEM demonstrated that the1MeV,1×1018/cm2electron irradiation could introduce damage near surface of GaN epitaxial layer.The dislocation densities were measured by XRD. It showed that1.7MeV and1MeV electron irradiation could increase the screw dislocation densities.