Evidence of relationship between mechanical stress and leakage current in AlGaN/GaN transistor after storage test

In this paper, leakage current signatures in AlGaN HEMT are studied after storage at 300°C. By comparing gate pad topology and by localized FIB cuts, Optical Beam Induce Resistance Change (OBIRCh) analysis was used to localize current path. Results tend to indicate that mechanical stresses in the gate structure strongly influences the leakage current of the transistor. Electrical characterization of the gate to source diode over temperatures supports the discrimination of the conduction mechanisms like thermionic field emission, Fowler-Nordheim or Poole-Frenkel. The OBIRCh analysis technique, widely used in silicon technology, appears to be a very efficient tool to localize leakage paths, in particular for HEMT topology with source terminated field plate.