C-DLTS interface defects in Al0.22Ga0.78N/GaN HEMTs on SiC: Spatial location of E2 traps

The purpose of this paper has focused on the investigation of the High electron mobility transistors AlGaN/GaN HEMTs based on SiC substrates by means of capacitance-voltage-temperature (C-V-T) and Deep Level Transient Spectroscopy (DLTS). The C-V analysis have been recorded in the 20-320 K temperature range and exhibit an increase in the pinch-off voltage by an amount of 300 mV once the temperature exceeds 200 K. A hysteresis phenomenon has been observed in the C-V spectra by sweeping the gate voltage Vgs forth and back between −5 and 0 V. This parasitic effect has identified to be related to trapping and detrapping mechanisms occurring in the GaN-HEMT device. DLTS results have proved the presence of two traps, labeled E1 and E2, with activation energies of 0.31eV and 0.525eV and capture cross sections of 3.86 × 10−18cm2 and 2.75 × 10−15cm2, respectively. The major E2 trap seems to be nitrogen anti-sites, possibly located in the buffer layer near to the interface AlGaN/GaN. It has been reported that there exists a good correlation betwixt the anomalies in C-V-T characteristics and DLTS measurements.