(American Institute of Physics, 2012) Wang, Xinwei; Saadat, Omair I.; Xi, Bin; Lou, Xiabing; Molnar, Richard J.; Palacios, Tomás; Gordon, Roy
Polycrystalline, partially epitaxial (Sc_2O_3) films were grown on AlGaN/GaN substrates by atomic layer deposition (ALD). With this ALD (Sc_2O_3) film as the insulator layer, the (Sc_2O_3)/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors showed excellent electrical performance with a high I({on})/I({off}) ratio of over 10(^8) and a low subthreshold slope of 75 mV/dec. The UV/NH(_4)OH surface treatment on AlGaN/GaN prior to ALD was found to be critical for achieving these excellent figures. In addition, the (Sc_2O_3)dielectric is found to be negatively charged, which facilitates the enhancement-mode operation. While bare (Sc_2O_3) suffers from moisture degradation, depositing a moisture blocking layer of ALD (Al_2O_3) can effectively eliminate this effect.
