Efficient Passivation of InP in Liquid Ammonia – EPINAL

The control of surface chemistry or interface is one of the key steps in the control of nanotechnology and photonics industry for high added values components. This fact is generally observed for the III-V semiconductors (III-Vs) where it is still difficult to achieve their exceptional performances predicted by physics.

The EPINAL program is based on a passivation involving a total rate covering of the surface of InP by an ultra thin film of polyphosphazene. This is an original and novel passivation route that the Consortium wants to extend to other III-V semiconductors. This process involves a controlled chemistry of nanoscale "P-N" bonds which is achieved by electrochemistry or electroless procedure in liquid ammonia ( 55 °C, atmospheric pressure). EPINAL is a multidisciplinary project combining 4 academic research groups (ILV, C2N, ICMPE and IRDEP). This highly contrasted but complementary multidisciplinary approach (chemistry, electrochemistry, physics and optics) is an original and innovative way to define the better performances of passivation films on III-Vs semiconductors. EPINAL aim is the understanding of fundamental modifications observed at the interface in order to reveal the best passivation as possible.

The preliminary results obtained by the consortium have been encouraging on InP surface by electrochemistry. The film formation has been indeed obtained in a fully controlled way by electrochemistry (thickness, homogeneity and spatial distribution). The chemical stability of the film on different solvents and its thermal stability have been revealed. The functionalisation of the film by inorganic fragment complexation has been observed and the
possibility to extend this passivation to pattern formation has been shown using SiO2 masks.

This passivation will also explore other III-Vs involving new “V-N” bonds such as “Sb-N” and “Ga-N” that are present in many ternary and quaternary alloys. The success of this extended passivation to other III-Vs semiconductors would allow many applications in the field of microelectronics and optoelectronic devices. Examples include passivation on the cleaved or engraved surfaces of SC waveguides to improve their resistance in high optical power densities. High-reflectivity treatments of mirror faces to increase laser performance are also essential. Passivation and isolation of laser ribbons for deep wave peak waveguide technology are other examples.