Metal?Oxide?Semiconductor Interface and Dielectric Properties of Atomic Layer Deposited SiO2 on GaN

The dielectric and MOS interface properties of SiO2 deposited with atomic layer deposition (ALD) on GaN with different surface treatments have been investigated with DC current–voltage (I–V) measurements and UV-assisted capacitance–voltage (C–V) measurements. Dielectric breakdown characteristics and leakage conduction mechanism for ALD SiO2 depend on surface conditions. Dry etch with NaOH post-etch GaN surface exhibited high oxide breakdown voltage with small distribution, larger barrier height characteristics, and higher charge to breakdown characteristics when compared with un-etched surface condition and dry etch with tetramethylammonium hydroxide (TMAH) post-etch surface condition. Moreover, fixed charge density and interface trap density at MOS interface extracted by UV-assisted C–V were comparable between un-etched surface sample and dry etch with NaOH post-etch surface sample, indicating dry etching damage recovery and demonstrating the usability of NaOH post-etching treatment. Comparison has also been made to a composite oxide of SiO2/Al2O3/SiO2, showing possibility of oxide charge engineering toward positive threshold voltage but carrier trapping by insertion of Al2O3.