Fe-doping starting depth impacts on static and transient characteristics of AlGaN/GaN HEMTs

Abstract

The Fe-doping starting depth impacts on static and transient characteristics are investigated in two AlGaN/GaN HEMT structures (HEMT-1 and HEMT-2). The compensational Fe-doping in the GaN buffer layer starts at 0.5 μm distance from the channel top edge in HEMT-1, while the Fe-doping originates at 0.7 μm depth from the channel in the HEMT-2. The HEMT-2 has shown promising results, such as high drain current, low current collapse, absence of kink effect, and relatively smaller subthreshold slope, than HEMT-1 at the expense of high gate leakage current. These findings reveal that the Fe-doping introduction 0.7 μm away from the channel can properly balance the 2DEG confinement and the buffer trapping effects. The drain current transient (DCT) results indicate slow trapping and detrapping dynamics for the Fe-related defect and reduced signal amplitude (mitigated trapping) in HEMT-2, compared to HEMT-1. The DCT outcomes are consistent with output-admittance (Y₂₂) parameters.