The effect of excess phosphorus vapor during the process of MIS structures on InP is analyzed in detail. It is shown that the density of interface state distribution is considerably modified after in situ thermal precleaning of the substrate in phosphorus overpressure (suppression of the Fermi-level pinning and significant reduction of the density of surface states near midgap). Phosphorus overpressure also provides an efficient protection of the surface during the insulator deposition. Fermi-level pinning in the upper part of the gap is assigned to the uncontrolled native oxide left on the surface after a stay of InP substrate in ambient atmosphere.

Reduction of the concentration of slow insulator states in SiO2/InP metal-insulator semiconductor structures J. Vac. Sci. Technol. B 5, 523 (1987); 10.1116/1.583943Evidence for interfacial defects in metalinsulatorInP structures induced by the insulator deposition A significant improvement of the electronical properties ofmetal-Al z 0 3 -InP structures is obtained after treating InP substrates at 500 °C in an As overpressure (10-6 Torr). The density of fast interface states near the conduction-band edge is markedly reduced and drift phenomena are greatly suppressed. as compared to results obtained with chemically etched reference substrates. An interpretation of these effects is given based on the compensation of phosphorus vacancies by As atoms more strongly attached to the InP surface than P atoms.InP metal-insulator-semiconductor field-effect transistors (MISFET's) are expected to playa major role in the fields of microwave power generation, high-speed logic circuits, and integrated optoelectronics. The demonstration of the potential of InP for the fabrication of inversion mode MISFET's, first reported by Lile et al. I has been confirmed since by many authors and for a wide variety of technological approaches. Despite these promising results it appears that several outstanding problems remain to be solved. For example, it is well-known that the InP surface cannot be 761

Two passivation treatments of InP surface are presented: (i) thermal treatment under an arsenic partial pressure by molecular-beam epitaxy technique, and (ii) a new As-based aqueous chemical treatment. Both result in similarly improved electronic and physicochemical properties of the InP surface. The fast interface state density is reduced, the drift phenomena are practically suppressed and the thermal stability is greatly enhanced.

Experiments were conducted on two types of GaAs substrates according to the surface treatment which either resulted in oxidation of the substrate (chemical etching) or in nearly oxygen-free interface (exposure of the substrate to a hydrogen/nitrogen mixture plasma). Owing to appropriate choices of the sequences of technological steps in the preparation of MIS samples, which include substrate treatment, deposition of the insulator (alumina obtained by reactive evaporation), and high temperature anneal (around 550 °C), it is given evidence of the great importance of the high temperature annealing step, solely responsible for the observed improvement in the electrical properties of the interface (as derived from capacitance and conductance measurements).