Quantitative characterization of interface traps in Al2O3/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors by dynamic capacitance dispersion technique

Abstract

In this letter, the interface traps of Al2O3/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were characterized quantitatively by dynamic capacitance dispersion technique. An analysis of Al2O3/AlGaN interface states demonstrated deep traps in the range of 0.53 eV-1.16 eV below the conduction band, with trap density nearly constant and two orders of magnitude smaller than that at AlGaN surface due to the use of atomic layer deposition-grown Al2O3 insulator. As much as 2.23 × 1013 eV−1 cm−2 fast traps with time constant smaller than 0.3 μs were observed at AlGaN/GaN interface of MOS-HEMTs, which was consistent with the qualitative prediction from pulsed I-V test.

Investigation of trap states in high Al content AlGaN/GaN high electron mobility transistors by frequency dependent capacitance and conductance analysis

“…5(a). However, in other reports involved low Al content structures, 13,15 trap time constant decreases with an increase in voltage. This conflict was explicated by referring to the one dimensional simulation of band diagram and electric field, which was derived from the self-consistent solutions of one dimensional Schrodinger and Poisson's equations.…”

“…The parallel conductance vs frequency and voltage was mapped and further investigation gave the time constant of trap states and trap profile. Much faster surface states and different law of time constant were extracted in this work compared to the previous studies, 13,[15][16][17] • C for 30 s. Ohmic contact resistance of 0.36 · mm and sheet resistance of 490 /sq were derived from transmission line models. The 60-nm SiN layer was deposited by plasma-enhanced chemical vapor deposition for surface passivation.…”

“…Capacitance meters generally assume the device to consist of the parallel C m -G m combination. A comparison of equivalent circuit of HEMTs with interface traps to the measured circuit gives G p /ω in terms of the measured capacitance C m , the device capacitance at accumulation region C ac , and the measured conductance G m as, 13,16,17 Fig. 3 demonstrates the measured capacitance versus frequency characteristics.…”

“…With voltage increasing, E FS at interface approaches BCB, so there is a decrease in τ it . 13 However, with high Al content barrier, more serious band bending and stronger electric field exist at the interface and barrier, so it is possible for electrons captured in trap states to tunnel into the 2DEG channel. Defining τ T as the tunneling time, the de-trapping time of trap states, i.e.…”

“…Surface states with time constant of (0.09-0.12) μs were found in S-HEMTs, and electron tunneling rather than emission was deemed to be the dominant de-trapping mechanism due to the high electric field in high Al content barrier. The density of surface states evaluated in S-HEMTs was (1.02-4.67)×10 13 AlGaN/GaN high electron mobility transistors (HEMTs) are attractive candidates for use in high voltage, high frequency, and high power applications due to the excellent material properties, while large off-state leakage and current collapse caused by surface or/and interface trap states have always been two of the most critical factors that restricted the device performance and reliability of GaN-based HEMTs. [1][2][3][4] With device size scaled down for higher frequency performance, high Al content (>40%) barrier is desirable for power levels as high as possible.…”