Preparation electrical properties and interface studies of plasma nitride layers on n-type InP

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Abstract
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 PxNyClz 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 °C with growing rates of 50 Å/min and stabilized by a post annealing at 300 °C in a reducing gaseous atmosphere. The optimized composition corresponds to Eg=5.5 eV, εr=6.2, n=1.95, a room-temperature resistivity ρ≳1013 Ω cm and a breakdown voltage Er≳5×107 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 Nis and of their energy distribution Dis(E). This interface states energy distribution Dis(E) is in the 1011 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 °C, this is at least 300 ° higher than with sulfides.