Solution‐Processed‐ZnO‐Mediated Semiconductor Bonding with High Mechanical Stability, Electrical Conductivity, Optical Transparency, and Roughness Tolerance

Abstract

Semiconductor bonding mediated by a transparent conductive oxide, ZnO, prepared by a simple solution spin‐on process, is presented. The ZnO synthesis, sintering, and bonding processes are realized in a single step, thus providing a highly efficient semiconductor bonding method. The ZnO‐mediated bonds simultaneously exhibit high mechanical stability, electrical conductivity, and optical transparency. The bonding's high tolerance for the roughness of the surfaces to be bonded is also demonstrated, due to the soft, deformable interfacial contact agent that is solidified in the bonding process, in contrast to direct bonding and bonding mediated by solid‐state materials. Furthermore, the fabrication and operation of solar‐cell devices are demonstrated using the developed ZnO‐mediated bonding technique, with current paths across the bonded interfaces, thus verifying the practical applicability of the bonding scheme. The developed ZnO‐mediated bonding scheme leads to low‐cost, high‐performance heterostructured optoelectronic device fabrication and integration.

Strain relaxation in semiconductor wafer bonding

“…For the above calculations for wafer bonding, the heterointerface was assumed to be fully covalently bonded, and treated in the same manner as the case of epitaxial growth. However, practical wafer-bonding schemes include not only direct semiconductor bonding but also bonding with interfacial agents such as oxides, 14,44,45) metals, [46][47][48] and organic materials. [49][50][51][52] Even for the direct semiconductor wafer bonding scheme, some amorphous layers are often observed to form between the bonded wafers.…”

Semiconductor Wafer Bonding for Solar Cell Applications: A Review

“…For the purpose of acquiring higher electrical conductivity and surface roughness tolerance than the case of semiconductor-to-semiconductor direct wafer bonding, transparent conductive oxide (TCO) materials, such as indium tin oxide, zinc oxide, and indium zinc oxide, have been considered as bonding agents for photovoltaic applications. [167][168][169][170][171] Nevertheless, TCO-mediated bonding can cause optical loss due to the refractive-index contrast between the semiconductor and TCO. As a rough estimate, a single semiconductor/TCO interface would have a reflectivity of 16% for refractive indices of 3.5 and 1.5, respectively.…”

Porous ZnO Microspheres Grafted with Poly‐(N‐isopropylacrylamide) via SI‐ATRP: Reversible Temperature‐Controlled Switching of Photocatalysis**

“…ZnO, with a band gap (3.37 eV at 300 K) and a large excitation binding energy (60 meV), [1,2] is considered a promising semiconductor material for potential use in energy generators, [3] gas sensors, [4] optical and electronic devices, [5] solar cells [6] and photocatalysts, [7] due to its cost‐effective, biocompatibility, [8] high mechanical, [9] thermal and chemical stability, [10] and unique optoelectronic, [11] piezoelectric, [12] photochemical [13] and catalytic properties [14] . Comparable to TiO 2 , ZnO exhibits similar properties but low‐cost, easier synthesis process, more absorption efficiency and higher electron mobility [15–18] .…”