Low-index nanopatterned barrier for hybrid oxide-free III-V silicon conductive bonding

Abstract

Oxide-free bonding of a III-V active stack emitting at 1300-1600 nm to a silicon-on-insulator wafer offers the capability to electrically inject lasers from the silicon side. However, a typical 500-nm-thick silicon layer notably attracts the fundamental guided mode of the silicon + III-V stack, a detrimental feature compared to established III-V Separate-Confinement Heterostructure (SCH) stacks. We experimentally probe with photoluminescence as an internal light source the guiding behavior for oxide-free bonding to a nanopatterned silicon wafer that acts as a low-index barrier. We use a sub-wavelength square array of small holes as an effective "low-index silicon" medium. It is weakly modulated along one dimension (superperiodic array) to outcouple the resulting guided modes to free space, where we use an angle-resolved spectroscopy study. Analysis of experimental branches confirms the capability to operate with a fundamental mode well localized in the III-V heterostructures.

PT-symmetry of multimode waveguides: A tool for multichannel communication

“…To add gain or loss to such a system, one could recourse to hybrid oxyde-free bonded silicon/3-5 structures [15,16] operating with gain from the InP-based 3-5 for instance. We use 2N = 6 stripes as in Fig.…”

Broad working bandwidth and “endlessly” single-mode guidance within hybrid silicon photonics

“…We can now wonder whether we can compensate also for the vertical swelling (as well as manage dispersion) by getting closer to the original fiber endlessly single-mode concept: to this end we cannot afford a thicker silicon (a vertical TE1 mode would appear), but we can attempt to surround the central core by "allowed modes" in the z-direction as well, not only in the SOI xy plane. This is similar to the low-index "horizontal slot" of [5][6][7], albeit with less index contrast: this option is made possible in the moderate index contrast regime by the advent of hybrid oxide-free InP-on-Si silicon photonics, whereby bonding of a III-V heterostructure (InP-based) to nanostructured silicon has been demonstrated [20,21].…”

“…In Fig. 2(a), we fill the grooves with a composite air-silicon material of index n EMTd λ, EMT referring to "effective material theory" [8,[20][21][22], and d to "dispersive": a broad range of indices can be made by nano-pattering silicon at modestly sub-wavelengths scales. We refer for simplicity to these dispersive media by the index n EMT for n Si 3.5 exactly 3.5 n Si 1.343 μm, i.e., we use n EMTd λ 1 n EMT − 1n Si λ − 1∕3.5 − 1 with fixed n EMT .…”

“…5(b), with a thicker silicon slab (700 nm) with 50/50 duty cycle grooves identical in shape to those of [b] above. It consists of an extra 400-nm-thick InP layer (index n ≈ 3.17 [20]), with a 300-nm top-quaternary layer (GaInAsP alloy with bandgap wavelength < 1.42 μm) having the same index as Si for simplicity. No patterning is made in these layers.…”