Interface characterization of Al2O3/m-plane GaN structure

The interface properties of Al2O3/GaN structures fabricated on the homo-epitaxial m-plane GaN were investigated. An atomically flat surface with a root mean square roughness of 0.15 nm was observed for the m-plane GaN layer on a substrate inclined 5 degrees toward the [000-1] direction. Even for the as-prepared sample, we obtained relatively low state densities of less than 3 x 10(11) cm(-2) eV(-1) at the Al2O3/m-plane GaN interface. A possible mechanism for such low interface state densities was discussed in correlation with the Ga-N dimer on the m-plane GaN surface. The post-metallization annealing process at 300 degrees C realized excellent capacitance-voltage (C-V) characteristics without frequency dispersion, further lowering state densities to 1.0 x 10(10) cm(-2) eV(-1)-2.0 x 10(10) cm(-2) eV(-1). In addition, the present Al2O3/m-plane GaN diode showed stable interface properties at high temperatures. Neither the flatband-voltage shift nor the frequency dispersion was observed in the C-V characteristics measured at 200 degrees C. Furthermore, current-voltage characteristics with relatively low leakage current in the order of 10(-9) A/cm(2) remained almost unchanged at temperatures up to 200 degrees C.

Automated summary

The interface properties of Al2O3/GaN structures fabricated on homo-epitaxial m-plane GaN were investigated, revealing low state densities and stable characteristics at high temperatures. The post-metallization annealing process further lowered state densities, and the Al2O3/m-plane GaN diode showed stable interface properties even at temperatures up to 200 degrees C.