Influence of AlN nucleation layer on vertical breakdown characteristics for GaN-on-Si

A study of metal-organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on breakdown characteristics for GaN-on-Si is presented. It is widely believed that AlN NL can act as an insulator because of its large band gap approximate to 6.2eV. On contrary, this study of AlN NL/Si reveals conductive nature and shows high vertical leakage. The structural examinations along with electrical characterization show AlN NL/Si quality depends on the growth temperature. The surface morphology and presence of unintentional oxygen impurities govern the vertical leakage of AlN NL/Si. Interestingly, the AlN NL influences the growth of subsequent epitaxial layers as well as their vertical breakdown voltages (BVs). Further, it is found that AlGaN intermediate layer and multipairs of AlGaN/AlN strained layer superlattice (SLS) grown over AlN NL with better surface properties enhances the vertical BV. A high BV of 1.3kV is achieved for SLS multipairs with a total thickness of 4.4m and the translated breakdown field strength is 2.8MVcm(-1) for MOCVD grown GaN-on-Si.