PREPARATION ELECTRICAL-PROPERTIES AND INTERFACE STUDIES OF PLASMA NITRIDE LAYERS ON N-TYPE INP

The growing conditions and the basic electronic and interface properties of InP-nitride-metal structures formed by indirect plasma-enhanced nitridation are reported. The deposited nitride layer P(x)N(y)Cl(z) is a NP polymer with a chemical composition close to P3N5 but with weak inclusions of H atoms. These nitride films are deposited at temperatures as low as 220-250-degrees-C with growing rates of 50 angstrom/min and stabilized by a post annealing at 300-degrees-C in a reducing gaseous atmosphere. The optimized composition corresponds to E(g) = 5.5 eV, epsilon-r = 6.2, n = 1.95, a room-temperature resistivity-rho > 10(13) OMEGA cm and a breakdown voltage E(r) > 5 x 10(7) V cm-1. The capacitance-voltage characteristics of Au-NP-InP diodes reveal that quasi-flat band and strong depletion regimes are reached, i.e., that the Fermi level in InP is swept through the entire upper half part of the electronic gap. These C-V characteristics are hysteresis free, and this allows a meaningful calculation of the interface states density N(is) and of their energy distribution D(is)(E). This interface states energy distribution D(is)(E) is in the 10(11) cm-2 eV-1 range and is very similar in magnitude to the ones observed at the InP-oxide or InP-sulfide interfaces despite the large differences in the growing atmospheres. The thermal stability of the InP-NP interface, as checked by inspection of the I-V and C-V curves, is good till 500-degrees-C, this is at least 300-degrees higher than with sulfides.