Search

The dc and power characteristics of AlGaN/GaN MOS-HEMTs with Sc2O3 gate dielectrics were compared with that of conventional metal-gate HEMTs fabricated on the same material. The MOS-HEMT shows higher saturated drain–source current (∼0.75 A/mm) and significantly better power-added efficiency (PAE, 27%) relative to the HEMT (∼0.6 A/mm and ∼5%). The Sc2O3 also provides effective surface passivation, with higher drain current, lower leakage currents and higher three-terminal breakdown voltage in passivated devices relative to unpassivated devices. The PAE also increases (from ∼5% to 12%) on the surface passivated HEMTs, showing that Sc2O3 is an attractive option for reducing gate and surface leakage in AlGaN/GaN heterostructure transistors. [Copyright &y& Elsevier]

Pt contacted AlGaN/GaN high electron mobility transistors with Sc2O3 gate dielectrics show reversible changes in drain–source current upon exposure to H2-containing ambients, even at room temperature. The changes in current (as high as 3 mA for relatively low gate voltage and drain–source voltage) are approximately an order of magnitude larger than for Pt/GaN Schottky diodes and a factor of 5 larger than Sc2O3/AlGaN/GaN metal–oxide–semiconductor (MOS) diodes exposed under the same conditions. This shows the advantage of using a transistor structure in which the gain produces larger current changes upon exposure to hydrogen-containing ambients. The increase in current is the result of a decrease in effective barrier height of the MOS gate of 30–50 mV at 25 °C for 10% H2/90% N2 ambients relative to pure N2 and is due to catalytic dissociation of the H2 on the Pt contact, followed by diffusion to the Sc2O3/AlGaN interface. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrated that Sc[sub 2]O[sub 3] thin films deposited by plasma-assisted molecular-beam epitaxy can be used simultaneously as a gate oxide and as a surface passivation layer on AlGaN/GaN high electron mobility transistors (HEMTs). The maximum drain source current, I[sub DS], reaches a value of over 0.8 A/mm and is ∼40% higher on Sc[sub 2]O[sub 3]/AlGaN/GaN transistors relative to conventional HEMTs fabricated on the same wafer. The metal-oxide-semiconductor HEMTs (MOS-HEMTs) threshold voltage is in good agreement with the theoretical value, indicating that Sc[sub 2]O[sub 3] retains a low surface state density on the A1GaN/GaN structures and effectively eliminates the collapse in drain current seen in unpassivated devices. The MOS-HEMTs can be modulated to +6 V of gate voltage. In particular, Sc[sub 2]O[sub 3] is a very promising candidate as a gate dielectric and surface passivant because it is more stable on GaN than is MgO. [ABSTRACT FROM AUTHOR]