Gate leakage/breakdown mechanism in unpassivated AlGaN∕GaN high electron mobility transistors (HEMTs) is investigated by performing temperature-dependent pulsed current–voltage (I–V) and current transient measurements of AlGaN∕GaN HEMTs without and with annealing after Schottky gate formation. After post-gate annealing, the devices exhibited significantly smaller gate leakage current and higher breakdown voltage even without any gate dielectrics or passivation layer. The temperature-dependent current transient measurements show that the current dispersion in the unannealed HEMTs is attributed to traps with an emission time constant (tE) of ∼0.5μs at 295 K and an activation energy of ∼38meV. On the contrary, the 20-min annealed devices have traps with tE of 21.6μs at 295 K and an activation energy of ∼0.31eV. The results suggest that the post-gate annealing removes shallow traps, and creates or activates deeper traps. We propose that the breakdown and gate leakage current is mainly due to the emission current from shallow traps in unpassivated AlGaN∕GaN HEMTs. The breakdown voltage improvement after the post-gate annealing is due to the removal of shallow traps near the Schottky gate metal∕AlGaN interface.

Influence of AlGaN barrier thickness on electrical and device properties in Al0.14Ga0.86N/GaN high electron mobility transistor structures J. Appl. Phys. 112, 053718 (2012) The inter-sublevel optical properties of a spherical quantum dot-quantum well with and without a donor impurity J. Appl. Phys. 112, 053717 (2012) Observation of a 0.5 conductance plateau in asymmetrically biased GaAs quantum point contact Appl. Phys. Lett. 101, 102401 (2012) Carrier control and transport modulation in GaSb/InAsSb core/shell nanowires Appl.

No abstract

No abstract

The Ni∕AlGaN interfaces in AlGaN∕GaN Schottky diodes were investigated to explore the physical origin of postannealing effects in AlGaN∕GaN heterostructures using electron beam induced current (EBIC) and current-voltage characteristics. Black spot density in EBIC images of as-deposited Ni∕AlGaN∕GaN diodes is in the same order of 108cm−2 as the dislocation density of AlGaN∕GaN heterostructures characterized by atomic force microscopy, indicating that recombination sites near Ni∕AlGaN interface are related to dislocations. The EBIC images of the annealed diodes showed that the postannealing reduced the electrically active states at the Schottky metal/AlGaN interfaces. The thermal reaction near Ni∕AlGaN interface due to the postannealing induced passivation effect, leading to decrease in reverse leakage current density, ideality factor, and saturation current density of the diodes and increase in the Schottky barrier height. We suggest that the postannealing process is an effective way to passivate the AlGaN∕GaN heterojunction field effect transistors.