In this work, we report a study of the temperature dependent pulsed current voltage and RF characterization of [Formula: see text]-(Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 hetero-structure FETs (HFETs) before and after silicon nitride (Si 3 N 4 ) passivation. Under sub-microsecond pulsing, a moderate DC-RF dispersion (current collapse) is observed before passivation in gate lag measurements, while no current collapse is observed in the drain lag measurements. The dispersion in the gate lag is possibly attributed to interface traps in the gate–drain access region. DC-RF dispersion did not show any strong dependence on the pulse widths. Temperature dependent RF measurements up to 250 °C do not show degradation in the cutoff frequencies. After Si 3 N 4 deposition at 350 °C, a shift of the threshold voltage is observed which changed the DC characteristics. However, the current collapse is eliminated; at 200 ns pulse widths, a 50% higher current is observed compared to the DC at high drain voltages. No current collapse is observed even at higher temperatures. RF performance of the passivated devices does not show degradation. These results show that ex situ deposited Si 3 N 4 is a potential candidate for passivation ofmore »
Temperature-induced local and average structural changes in BaTiO 3 − x Bi(Zn 1/2 Ti 1/2 )O 3 solid solutions: The origin of high temperature dielectric permittivity
More Like this
-
-
-
(Bi 1/2 Na 1/2 )TiO 3 (BNT) based ceramics have been the hot topic for a few years because of their multiple functions, from the piezoelectric properties to more recently the electrostatic energy storage performance. However, some basic issues are still unclear, preventing their wide application in real devices. One of them is the underlying conduction mechanism, the interplay of electronic and ionic carriers as a mixed ionic case and the subsequent quantification. This paper deals with the most basic compositions, which are the typical ones from the (1 − x )(Bi 1/2 Na 1/2 )TiO 3 – x BaTiO 3 (BNT– x BT) phase diagram. The conductivity is primarily investigated by impedance spectroscopy, while different equivalent circuits are applied to different conduction mechanisms. A transition from predominantly ionic to predominantly electronic conduction is revealed to occur with the increase in BaTiO 3 concentration. The mixed ionic–electronic conduction in the composition near the morphotropic phase boundary, namely BNT–7%BT, is identified and then quantified. To verify our interpretation of impedance results, dc degradation is, for the first time, conducted in this family of materials, from which the electronic and ionic conductions can be easily separated by accessing the mean time tomore »
