Junction properties of homoepitaxial diamond films grown by step–flow mode

Abstract

Homoepitaxial diamond films with atomically flat surface were reproducibly grown by step–flow mode under the condition of less than 0.1% CH4/H2. Using these diamond films, high-quality Schottky junctions between Al and high-conductivity layer near the surface of the films have been successfully made. At 400 K, the ideality factor and the barrier height of the Schottky junctions, which are defined by the conventional junction theory, estimated from the current–voltage (I–V) characteristics are about 1.1 and 1.5–1.6 eV, respectively. Under the condition of more than 0.1% CH4/H2, however, many unepitaxial crystallites (UC) and pyramidal hillocks (PH) are often formed on the surface of the films which are even mainly grown by the step–flow mode. The Schottky junction properties become worse with an increase in the density of UC and PH. In particular, the increase in the saturation current, which was obtained by extrapolating the straight line to V=0 in a plot of ln I against V, correlated with Schottky barrier height is more sensitive than that of the ideality factor to the density of UC and PH. It is concluded that diamond films grown by the step–flow mode without UC and PH is essential to obtain an ideal Schottky junction.