Surface potential measurements on Ni–(Al)GaN lateral Schottky junction using scanning Kelvin probe microscopy

Abstract

The surface potential distribution across lateral Ni–(Al)GaN Schottky junctions was measured by scanning Kelvin probe microscopy. The bare surface barrier heights of unintentionally doped Al0.22Ga0.78N and n-GaN in air were estimated to be ∼1.15 and 0.7 eV, respectively. Upon 364.5 nm (band edge for GaN) illumination, the surface barriers of both n-GaN and AlGaN∕GaN were observed to decrease. The minority carrier diffusion length in n-GaN(Si∼3.5×1017cm−3) was extracted from the surface photovoltage profile near the Schottky junction, ∼1.8±0.4μm. The scanning Kelvin probe surface photovoltage technique for measuring minority carrier diffusion length, while similar to the electron beam induced current technique, offers greater accuracy and higher spatial resolution due to separation of the minority carrier excitation source (relatively large area, above band gap light beam) from the nanometer-size probe (scanning force microscope tip).