Investigation of vertical transport in n-GaN films grown by molecular beam epitaxy using Schottky barrier diodes

Abstract

In this letter, the lateral and vertical transport in lightly doped n−-GaN films, grown by plasma assisted molecular beam epitaxy, were investigated in order to explore the role of electron scattering by charged dislocations. Lateral transport constants were determined by Hall effect measurements on n−-GaN films. The doping concentration and mobility of the investigated films was 1–2×1017 cm−3 and 150–200 cm2/V s, respectively. Vertical transport was studied by etching mesa structures and forming Schottky barrier diodes. The diodes exhibit near ideal forward current–voltage characteristics with reverse saturation current densities in the 1–10×10−9 A cm−2 range. The doping concentrations as well as the barrier height of the diodes were determined from capacitance–voltage measurements to be 8–9×1016 cm−3 and 0.95–1.0 V, respectively. The analysis of the reverse saturation current, using the diffusion theory, leads to vertical mobility values of 950 cm2/V s. The significant increase in mobility for vertical transport is attributed to reduction in scattering by charged dislocations.