Integration of the Ni/InP system on a 300 mm platform for III-V/Si hybrid lasers

Abstract

The integration of III-V/Si hybrid lasers on a 300 mm platform for photonic applications requires the development of dedicated CMOS-compatible contacts, for which nickel-based ones are very good candidates. In this scope, this work presents and compares the impact of in situ preclean based on argon (Ar) or helium (He) plasma on the surface integrity of InP prior to the nickel (Ni) contact deposition. The resulting surface morphology, element distribution, phase formation sequence of the Ni/InP system, and electrical behavior of Ni/n-InP contacts are detailed using morphological, structural, and electrical characterizations. The results show that Ar preclean significantly damages the InP surface by generating high roughness and creating indium (In) dots on the top surface, while He preclean seems to induce lighter damages and no In dots. Although the phase sequence of the Ni/InP system is overall the same for each preclean, the electrical behavior differs depending on the nature of the preclean. On one hand, Ni/n-InP Ar-precleaned contacts exhibit nonohmic behavior for each investigated thermal budget. On the other hand, He-precleaned contacts features ohmic behavior for the as-deposited state and thermal anneals up to 350°C for 60 s. They, however, become nonohmic after anneals of 400 and 450°C for 60 s. These results, hence, suggest that the difference of electrical behavior obtained between Ar and He-precleaned Ni/n-InP contacts is due to differences in the state surface and morphology.

Development of Ni₂P Contact Technology and Its Integration on III-V Materials for 300 mm Si Photonics Platform

“…Fig. 6 also shows a comparison between the electrical properties of the Ni 2 P/n-InP system and two other Ni-based contact metallizations previously investigated, namely Ni (square symbols) and Ni 0.9 Pt 0.1 (triangle symbols) [21], [33]. For all the systems, an initial metal thickness of 20 nm capped by a TiN layer was deposited on the n-InP layers.…”

“…The latter were fabricated using 300 nm doped epilayers (Si-doped n-InP, N d = 5 × 10 18 at.cm −3 or Zn-doped p-In 0.53 Ga 0.47 As with N a = 2 × 10 19 at.cm −3 ) on semiinsulating InP substrates. Transfer length measurement (TLM) structures were fabricated according to the procedure already described in previous works [23], [33] to extract the contact resistivity.…”

“…The study of the Ni / InP system [29]- [33] showed that several phases formed during the solid-state reaction of a Ni thin film with an InP layer. We recently demonstrated the following phase formation sequence [32], [33].…”

“…The study of the Ni / InP system [29]- [33] showed that several phases formed during the solid-state reaction of a Ni thin film with an InP layer. We recently demonstrated the following phase formation sequence [32], [33]. At low temperature, the Ni thin film was present along with an intermixing layer of Ni x InP in an amorphous state.…”

“…Beyond a threshold temperature, the system evolved towards a crystalline state where the coexistence of 3 phases was reported, namely Ni 2 P, Ni 3 P and Ni 2 InP. At higher temperatures, the agglomeration of Ni 2 P and In was evidenced and the contacts became nonohmic [22], [33]. To overcome this issue, a technological solution was proposed.…”