GaAs Metal–Oxide–Semiconductor Capacitor With Nd-Based High-k Oxynitrides as Gate Dielectric and Passivation Layer

GaAs metal-oxide-semiconductor capacitors with NdTaON as gate dielectric and NdAlON, NdON or AlON as interfacial passivation layer (IPL) are fabricated, and their interfacial and electrical properties are compared with their counterpart without IPL. Experimental results show that owing to the suppressed hygroscopicity of NdON by Al incorporation, best improvements in electrical properties and reliability are achieved for the sample with NdAlON IPL (low interface-state density (8 × 10
¹¹
cm
^-2
/eV), small flatband voltage (0.72 V), negligible hysteresis (43 mV), small frequency dispersion, and low gate leakage current density (2.56 × 10
^-6
A/cm
²
at V
_fb
+ 1 V). These should be attributed to suppressed growth of unstable Ga and As oxides on the GaAs surface and reduced in-diffusion of elements from the gate dielectric to the GaAs surface by the NdAlON IPL during gate-dielectric annealing.