III-V/Si Wafer Bonding Using Transparent, Conductive Oxide Interlayers

TL;DR

This paper introduces a low-temperature wafer bonding technique using a transparent, conductive oxide interlayer to connect III-V materials with silicon, enabling efficient optoelectronic devices like tandem solar cells.

Contribution

It demonstrates a novel plasma-activated bonding method with a TCO interlayer that maintains optical transparency and electrical conductivity at low temperatures.

Findings

Ohmic behavior observed at bonding temperatures 100-350°C

Contact resistivity below 1 Ωcm² at 200°C

Minimal parasitic light absorption in bonded structures

Abstract

We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100$^{\circ}$C to 350$^{\circ}$C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 $\Omega$cm$^2$ for samples bonded at 200$^{\circ}$C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga$_{0.5}$In$_{0.5}$P/Si tandem solar cells operating at one sun or low concentration conditions.