Impact of Film Stress of Field-Plate Dielectric on Electric Characteristics of GaN-HEMTs

Abstract

This article reports a systematic study focused on the mechanical stress effect of field-plate dielectric film on the electric characteristics of AlGaN/GaN high-electron mobility transistors (HEMTs). AlGaN/GaN HEMTs were fabricated on SiC substrates, where the stress of a SiN field-plate dielectric film ranged from -252 (compressive) to +26.5 (tensile) MPa. Si-rich and compressive SiN films exhibited a significant increase in the isolation leakage. On the other hand, relatively N-rich and tensile SiN films showed a significant increase in the gate leakage current of HEMTs. In addition, pulsed I-V measurements showed the suppression in the current collapse by increasing the tensile stress. Consequently, small current collapse and small gate leakage current were obtained simultaneously with good isolation, as the film stress was optimized.