Passivation
of InP and its devices by organic self-assembled monolayers (SAMs) of organic
thiols is presented. SAM’s on InP were characterized by FTIR, contact angle
measurements and Auger spectroscopy. It was found that the intensity of steady
state photoluminescence (PL) of n-type InP wafers covered with the thiolated
SAMs was significantly higher than that of bare wafers. Furthermore, the dark
current in I-V curves of metal-semiconductor-metal (MSM) diodes fabricated on
semi-insulated InP was one order of magnitude smaller for diodes coated with
the ultrathin layers. Similarly, a reduction by several orders of magnitude in
the leakage current of p-i-n avalanche photodiodes (APD) was observed upon
coating. The enhancement in photoluminescence intensity upon covering the
surface with thiolated SAMs, as well as the reduction in the dark current of
the devices, is explaned in terms of the reduction in the density of surface
states due to electrical passivation. The ease by which one can tailor the
outer functional groups of SAM’s provides a way to connect this new class of
passivators with standard encapsulators, such as polyimide, as demonstrated by
the wetting properties of modified surfaces. The passivating properties of
thiolated SAM, formed on InP surface and covered by well wetted polyimide
layer, was found to be stable at the relatively high temperature, at which the
polyimide is cured. In this way a possible compatibility between passivation by
thiolated SAMs and existing encapsulation process of InP devices was examined
