Abstract

AlGaN/GaN metalinsulatorsemiconductor heterostructure field effect transistors (MIS-HFETs) with recessed-gate geometry have been proposed to implement normally-off operation for power electronics applications. With this structure, two-dimensional electron gas (2DEG) density under the gate region was effectively depleted, thus controlling threshold voltage while maintaining low on-resistance and high current density. We found a strong correlation between recess depth and threshold voltage: the deeper recess etching provided the higher threshold voltage without any significant decrease in other device parameters such as drain current (90 and 76 mA/mm for 25 and 35 nm recess depths, respectively), subthreshold slope (0.36 and 0.42 V decade1), onoff ratio (106) and field effect mobility (66.7 and 58.3 cm2 V1 s1). We have also examined the electrical properties of the HFETs by employing multiple passivation layers. The drain current and breakdown voltage after multiple passivation layers (Al2O3 þ SiOx) were improved by approximately 34 % (from 135 to 180 mA/mm) and 40 % (from 335 to 470 V) compared to that after a single passivation layer (Al2O3 only), which is ascribed to the surface charge controlled effect. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3555069] All rights reserved. Manuscript submitted December 28, 2010; revised manuscript received January 24, 2011. Published March 1, 2011. AlGaN/GaN heterostructure field effect transistors (HFETs) have attracted much attention for high power and high frequency applica-tions due to their large breakdown field strength, high two-dimensional