Surface passivation with organothiolated self-assembled monolayers (SAMs) that form chemical bonds with the InP surface is described. Indium phosphide surfaces coated with thiolated SAMs were characterized by Fourier-transform infrared spectroscopy, contact angle measurements, and Auger spectroscopy. The steady state photoluminescence of InP wafers increased by a factor of 14 as a result of this surface passivation method. A decrease by one to two orders of magnitude in the dark currents of interdigitated metal-semiconductor-metal diodes and p-i-n photodiodes Was obtained. The option of using SAMs that are well-wetted by standard encapsulators such as polyimides and the thermal stability of the SAMs at the polymer's curing temperatures open the way to achieve high quality passivation and encapsulation, even when the electronic devices contain negative slope sidewalls or undercut cavities. (C) 2003 American Vacuum Society.