Deep-Level Traps in AlGaN/GaN- And AlInN/GaN-Based HEMTs with Different Buffer Doping Technologies

Deep-level traps in AlGaN/GaN- and AlInN/GaN-based HEMTs with different buffer doping technologies are identified by drain current transient spectroscopy (DCTS) and low-frequency (LF) output admittance ( {Y}_{{22}} ) dispersion techniques. TCAD simulations are also carried out to determine the spatial location and type of traps. The DCTS and LF {Y}_{{22}} measurements on Al_0.25Ga_0.75N/GaN HEMT (Fe-doped buffer) reveal a single electron trap at {E}_{C} - {0.47} eV. On the other hand, an electron trap at {E}_{C} - (0.53-0.59) eV and a deep hole trap at {E}_{V} + {0.82} eV are detected in Al_0.845In_0.155N/AlN/GaN HEMT with unintentionally doped (UID) buffer, while a slow detrapping behavior is noticed at {E}_{C} - {0.6} eV in Al_0.83In_0.17N/AlN/GaN HEMT with C-doped buffer. The DCTS and LF {Y}_{{22}} measurements yield nearly the same trap signatures, indicating the reliability of the trap characterization techniques used in this article. The simulated LF {Y}_{{22}} characteristics show that all these traps are acceptor-like states located in the buffer layer. The identified trap parameters in various buffers may be helpful to improve the crystalline quality of the epitaxial buffer layers.