(Invited, Digital Presentation) Outstanding Contributions of Liquid Ammonia on III-V Semiconductors (Photo)-Electrochemistry

Abstract

The control of the surface or interface chemistry is a key step for new industrial products with high added value. This is critical in the case of III-Vs for which it is still difficult to reach the exceptional performances that are predicted by the III-V’s physic. The III-V MOS have been singled out to be a future technology after silicon CMOS. However, the major difficulty lies in the surface or interface chemistry that is hardly controlled and often uncertain. So far, the surface engineering of III-Vs has not met the quality needed for high performances[1]. Thus for III-Vs like InP and related compounds, dry or wet treatments have been and still are explored. This research takes advantage of the remarkable properties of phosphazene (flexibility of the inorganic backbone, chemical stability...) to passivate III-V semiconductor surfaces. The strength and novelty are based on our capability to develop a polyphosphazene network controlled at the nanometric scale with good anchoring to the III-V lattice[2].This research concerns a fine-tuning of the surface at the nanometric scale allowing their potential use in III-V micro (opto)electronic. The tuning is based on a completely novel III-V surface chemistry inspired by the polyphosphazenes structures[3]. The innovation lies in a totally different (photo-electro)chemical engineering than the ones commonly used on III-Vs. Innovation also concerns the use of liquid ammonia (NH3 Liq.) as a solvent, it allows specific chemical processes on III-Vs, sheltered from water interaction, opening original routes for III-V surface treatment and advanced device fabrication processes. The use of NH3 Liq. is singular for the electronic industry but it is a classical industrial solvent and we claim that introduction of this novelty in the (opto)electronic industry would not be a limiting factor. Indeed NH3 Liq. as an efficient non-aqueous solvent provides ideal conditions for the treatment of semiconductor surface: the high purity (electronic grade quality) and the exclusion of residual active water molecules from the surface. This point is crucial since the formation of unsuitable oxide on the surface during the passivation process at the interface SC/liquid is therefore efficiently excluded. Often the uncontrolled development of superficial oxide seriously hampers the integration of III-Vs in the MOS sectors. In the case of InP semiconductors (for both types), our preliminary results have shown by XPS the electrochemical successful formation of a stable passivating “polyphosphazene like” ultra-thin film obtained by (photo)-electrochemistry in NH3 Liq. (Fig. 1 and 2). Using the phosphorus outers atoms of the InP lattice. As a consequence, the development of well-ordered polyphosphazene of surfaces is unique and very challenging. This research can offer appropriate surface structure design on passivated III-Vs. With this goal in mind, our preliminary results are promising. Indeed, ILV’s expertise in III-V treatments NH3 Liq. provides the formation of stable polyphosphazene on InP and GaP (Fig.3)[4]. Acknowledgements Continuation of this work will be supported by the French National Research Agency (ANR). [1] S.R. Morrisson, Electrochemistry at Semiconductor and Oxidized Metal Electrodes, Plenum Press, New York (1980). [2] A-M. Gonçalves, N. Mézailles, C. Mathieu, P. Le Floch, A. Etcheberry, Chem. Mat,. 22, (2010) 3114-3120. [3] H. R. Allcock, in Chemistry and Application of polyphosphazenes, (Eds: A. Willey and Sons), Willey-Interscience, USA (2003). [4] A-M Gonçalves, C. Njel, D. Aureau, A. Etcheberry. Appl Surf Sci 391 (2016) 44-48. Figure 1