Harvesting and Transferring Vertical Pillar Arrays of Single-Crystal Semiconductor Devices to Arbitrary Substrates

Abstract

Abstract-Development of devices that can be fabricated on amorphous substrates using multiple single-crystal semiconductors with different physical, electrical, and optical characteristics is important for highly efficient portable and flexible electronics, optoelectronics, and energy conversion devices. Reducing the use of single-crystal substrates can contribute to low-cost and environmentally benign devices covering a large area. We demonstrate a technique to harvest and transfer vertically aligned single-crystal semiconductor micro-and nanopillars from a singlecrystal substrate to a low-cost carrier substrate while simultaneously preserving the integrity, order, shape, and fidelity of the transferred pillar arrays. The transfer technique facilitates multilayer process integration by exploiting a vertical embossing and lateral fracturing method using a spin-coated polymer layer on a carrier substrate. Electrical contacts are formed using a bilayer of metal and conducting polymer such as gold (Au) and polyaniline (PAni). In this method, the original single-crystal substrate can be repeatedly used for generating more devices and is minimally consumed, whereas in conventional fabrication methods, the substrate is employed solely as a mechanical support. This heterogeneous integration technique potentially offers devices with low physical fill factor contributing to lower leakage current and noise, reduced parasitic capacitance, and enhanced photon-semiconductor interactions, and enables heterogeneous multimaterial integration such as silicon with compound semiconductors for rapidly expanding large-scale applications, including low-cost and flexible electronics, displays, tactile sensors, and energy conversion systems.Index Terms-Compound semiconductors, heterogeneous material integration, integrated multifunctional devices, micro/ nano-pillars, photon traps, vertical device arrays, 3-D material integration.

Electroassisted Transfer of Vertical Silicon Wire Arrays Using a Sacrificial Porous Silicon Layer

“…Separation of the resulting Si wire arrays from the parent Si wafer allows the electrical, thermal, optical, and mechanical properties of the Si wire arrays to be isolated and harnessed in devices without being overshadowed by the properties of the thick parent Si wafer and enables the transfer of the Si wire arrays to other flexible, lightweight, low cost, or transparent substrates for enhanced device functionality. A key requirement for the separation and transfer of Si wire arrays is the preservation of their original properties and orientation. − A range of methods have been developed for the separation of vertical Si wire arrays from their parent Si wafers, which rely on the mechanical breakage of the Si wires by the application of peeling forces, − direct shear forces, − or the creation of a horizontal porous crack within the Si wires. , However, these methods require that the Si wires are held together during the mechanical breaking process by encapsulation in a polymer host, the existence of which makes it difficult to use the separated Si wires for applications that require an exposed Si surface, such as for ohmic contacts to metal electrodes, sensors, or catalysts. In addition, some of these methods are only compatible with Si wires of certain geometries − or those made by particular methods. , To address these shortcomings, we have developed, and report herein, a new electroassisted transfer printing method for the transfer of vertical Si wire arrays from their parent Si wafers to other substrates without modification to the properties and orientation of the Si wires, without constraints on the Si wire geometry or fabrication method, and without the need for polymer encapsulation.…”

“…A key requirement for the separation and transfer of Si wire arrays is the preservation of their original properties and orientation. − A range of methods have been developed for the separation of vertical Si wire arrays from their parent Si wafers, which rely on the mechanical breakage of the Si wires by the application of peeling forces, − direct shear forces, − or the creation of a horizontal porous crack within the Si wires. , However, these methods require that the Si wires are held together during the mechanical breaking process by encapsulation in a polymer host, the existence of which makes it difficult to use the separated Si wires for applications that require an exposed Si surface, such as for ohmic contacts to metal electrodes, sensors, or catalysts. In addition, some of these methods are only compatible with Si wires of certain geometries − or those made by particular methods. , To address these shortcomings, we have developed, and report herein, a new electroassisted transfer printing method for the transfer of vertical Si wire arrays from their parent Si wafers to other substrates without modification to the properties and orientation of the Si wires, without constraints on the Si wire geometry or fabrication method, and without the need for polymer encapsulation. The fundamental understanding gained from this new electroassisted transfer method also enabled us to develop a current-induced metal-assisted chemical etching method for the facile and rapid synthesis of Si nanowires with axially modulated porosity.…”