Trapping effects on AlGaN/GaN HEMT characteristics

This paper describes device simulation studies of surface and buffer trapping effects on static I-V, output-admittance (Y₂₂), and transient characteristics of AlGaN/GaN HEMTs. The TCAD simulation model considering surface donors at E_C − 0.5 eV and buffer traps at E_C − 0.47 eV have been used to quantitatively reproduce the measured DC, Y₂₂ frequency dispersion, gate-lag (GL) and drain-lag (DL) transients of AlGaN/GaN HEMT with 0.25 µm gate length. Moreover, simulated GL and DL transient responses of AlGaN/GaN HEMT with a longer gate length (0.5 µm) are validated with the reported experimental results. The impact of barrier trap at E_C − 0.45 eV on the HEMT properties is also explored. It is shown that by matching simulation results with experimental data, it is possible to identify the trap (surface or buffer) responsible for a particular trapping induced degradation as well as its concentration and capture cross-section.