Short Term Reliability and Robustness of ultra-thin barrier, 110 nrn-gate AlN/GaN HEMTs

Abstract

Short-term reliability and robustness of 110 nm AlN/GaN HEMTs has been evaluated by means off-state, semi-on state and on-state step stress tests on devices having different gate-drain distance, LGD. While breakdown voltages and critical voltages scale almost linearly with LGD, failure mode remains almost unchanged in the nine device groups, and consists in an increase of gate leakage, accompanied by a positive shift of threshold voltage. In off-state, electroluminescence images detect the presence of localized leakage paths which may correspond to dislocations and act as preferential paths for electron trapping. Degradation is therefore preliminary attributed to hot-electron trapping, enhanced by electric fields.

Highly Homogeneous Current Transport in Ultra-Thin Aluminum Nitride (AlN) Epitaxial Films on Gallium Nitride (GaN) Deposited by Plasma Enhanced Atomic Layer Deposition

“…The inherent lattice mismatch, of about 2.4%, between the AlN and GaN crystal structures is responsible for a tensile strain in AlN films grown on GaN. The piezoelectric polarization associated with such tensile strain, combined with the spontaneous polarization of the AlN and GaN materials, results in the formation of a two-dimensional electron gas (2DEG) [8] at their interface, which can be exploited for the fabrication of AlN/GaN HEMTs suitable for RF applications [9][10][11][12]. Furthermore, high crystalline quality ultra-thin AlN layers on GaN have been recently employed as tunneling barriers of vertical hot electron transistors (HETs) with a graphene base, currently regarded as promising candidates for future ultra-high-frequency (THz) applications [13][14][15].…”

Evaluation of electroluminescence of AlGaN/GaN HEMT on free-standing GaN substrate

“…[12][13][14] Among these methods, EL is a simple and non-destructive method to indicate an area of the highest electric field. [14][15][16][17][18][19][20][21][22][23] So far, the EL in HEMTs has been investigated in terms of dependency of a device structure, including kinds of a passivation layer, with and without a GaN cap, and distance of gate-to-drain (L gd ). 14,17,20) Recently, our group found that a severe current collapse occurs at the same time of a shift of the EL from the gate electrode to the drain electrode of HEMTs on a SiC substrate (GaN-on-SiC) under an increased drain voltage (V ds ).…”

“…[14][15][16][17][18][19][20][21][22][23] So far, the EL in HEMTs has been investigated in terms of dependency of a device structure, including kinds of a passivation layer, with and without a GaN cap, and distance of gate-to-drain (L gd ). 14,17,20) Recently, our group found that a severe current collapse occurs at the same time of a shift of the EL from the gate electrode to the drain electrode of HEMTs on a SiC substrate (GaN-on-SiC) under an increased drain voltage (V ds ). 18,24) However, to our best knowledge, few reports studied the role of the substrate on the EL in HEMTs with a correlation to current collapse.…”