Correlation of device performance and defects in AlGaN/GaN high-electron mobility transistors

Abstract

Device performance and defects in AlGaN/GaN high-electron mobility transistors (HEMTs) have been correlated. Surface depressions and threading dislocations, revealed by optical-defect mapping and atomic force microscopy (AFM), compromised the effectiveness of the SiN x surface-passivation effect as evidenced by the gate-lag measurements. The residual carriers in the GaNbuffer layer observed from the capacitance-voltage depth profile have been attributed to the point defects and threading dislocations either acting as donors or causing local charge accumulations. Deep-level transient-spectroscopy measurements showed the existence of several traps corresponding to surface states and bulk-dislocation defects. The formation of electron-accumulation regions on the surface or (and) in the GaN-buffer layer was confirmed by currentvoltage measurements. This second, virtual gate formed by electron accumulations can deplete the channel and cause a large-signal gain collapse leading to degraded output power. A good correlation was established between the device performance and defects in AlGaN/GaN HEMT structure.

Deep levels in iron doped n- and p-type 4H-SiC

“…25) and the D-center (E V þ 0.62 eV) (Ref. 25) were observed. The evaluation of the B concentration is uncertain, since it exceeds the low concentration approximation limit (N t ( N d ).…”

“…1(b)), only the boron related peaks B (E V þ 0.27 eV) (Ref. 25) and the D-center (E V þ 0.62 eV) (Ref. 25) were observed.…”

Traps in AlGaN∕GaN∕SiC heterostructures studied by deep level transient spectroscopy

“…These studies have utilized several different characterization techniques, including photoionization spectroscopy, 1 drain leakage-current measurements, 2 transient drain current measurements at different temperatures, 3 and current-mode deep level transient spectroscopy ͑DLTS͒. 4 In the present investigation, we have employed capacitance-mode DLTS, using Schottky barrier diodes ͑SBDs͒ formed on the AlGaN. One benefit of using capacitance DLTS is that we can then compare the observed traps in the AlGaN/ GaN structure with commonly observed traps in GaN alone.…”

“…[7][8][9][10] This trap was also reported in AlGaN/ GaN HEMTs by measuring drain leakage current at different temperatures 2 and current DLTS. 4 On the other hand, trap A 2 can be induced by electron irradiation, simultaneously with another well-known trap, E ͑0.16 eV͒. Since trap E has been reliably assigned to the N vacancy, it seems reasonable that A 2 could be related to the N interstitial.…”

Electrical Characterization of Traps in AlGaN/GaN FAT-HEMT’s on Silicon Substrate by C-V and DLTS Measurements

“…To this end, research works have been undertaken in the subject of trapping effects with the use of different electrical characterization techniques, including photoionization spectroscopy [17], drain leakage-current measurements [18], current-deep level transient spectroscopy (CDLTS) [19] and deep level transient spectroscopy (DLTS) [20], Current-Voltage, I(V) [21] and Capacitance-Voltage C(V) measurements [22].…”