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

Kristelle Bougot-Robin,Henri Benisty,Anne Talneau

doi:10.1364/oe.22.023333

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.

Highlights

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
The interest of hybrid silicon photonics, with III-V active material bonded onto a platform such as Silicon-On-Insulator (SOI), is undisputed [1,2,3]
We show that a nanopatterned silicon consisting of an array of holes with a modest air fraction f acts as a low-index barrier between Si and EHS, and greatly assists laser operation in the established regime of III-V’s Separate Confinement Heterostructures (SCH)

Summary

Introduction

The interest of hybrid silicon photonics, with III-V active material bonded onto a platform such as Silicon-On-Insulator (SOI), is undisputed [1,2,3]. One first point was to get guidance from well mastered low-loss silicon structures, and to get active emission from the III-V epitaxial heterostructure stack (denoted EHS below), either in combination or for separate action, with a transfer in between For these optical functions, bonding can make use of oxide, or polymer (e.g., benzocyclobutene BCB). The stack’s fundamental mode (FM) may widely overlap the Si slab, a penalty for a laser structure, as the confinement factor ΓFM of the active quantum wells (QWs) is reduced To circumvent this penalty, we show that a nanopatterned silicon consisting of an array of holes with a modest air fraction f acts as a low-index barrier between Si and EHS, and greatly assists laser operation in the established regime of III-V’s Separate Confinement Heterostructures (SCH).

Sample and experimental set-up

Dispersion analysis

Dispersion characterization and discussion

Conclusion