Comparison of AlGaN/GaN HEMTs Grown and Fabricated on Sapphire Substrate with AlN and GaN Nucleation Layers

AlGaN/GaN heterostructure materials and HEMTs with AlN and GaN nucleation layers were grown and fabricated on sapphire substrates respectively. AlGaN/GaN heterostructure material with AlN nucleation layer shows lower dislocation densities than the counterpart sample with GaN nucleation layer verified by XRD omega-scan measurement. Oxygen impurity in the sample with AlN nucleation layer has a lower concentration proved by the SIMS profiles. The lower dislocation density and oxygen impurity concentration in AlGaN/GaN heterostructure material with AlN nucleation layer result in better device performance. AlGaN/GaN HEMT device with AlN nucleation layer shows three orders of magnitude lower leakage current than that with GaN nucleation layer. Pulse I-V characterizations suggest that traps in buffer have a less impact on the device with AlN nucleation layer.