Electrical and chemical stability of Al/SiN_x/InP–metal–insulator– semiconductor diodes with gas phase polysulfide exposure on InP

Releasing the Fermi‐level pinning of InP by gas phase polysulfide exposure has recently been demonstrated by surface charge spectroscopy [Lau et al., Surf. Sci. 271, 579 (1992)]. The present article reports a study of capacitance–voltage (C–V) measurements on metal–insulator–semiconductor (MIS) diodes fabricated using a process which includes this polysulfide passivation. The effectiveness of this passivation technique in reducing interface trap densities (D_it) was confirmed. The optimized MIS fabrication procedure involved (a) surface cleaning and polysulfide exposure; (b) immediate deposition of silicon nitride by remote plasma chemical vapor deposition (RPCVD); and (c) deposition of aluminum and annealing at 500 °C for 15 min in forming gas. The C–V results gave a D_it of 5×10¹⁰ cm⁻² eV⁻¹ via the Terman analysis and 5×10¹¹ cm² eV⁻¹ via the high–low frequency method. The MIS properties were unchanged after a two months air exposure and a one week 110 °C heating in air. It was also found that the replacement of aluminum with Ti/Pt/Au, and of RPCVD with plasma enhanced chemical vapor deposition all led to higher D_it values.