Buckled and Wavy Ribbons of GaAs for High‐Performance Electronics on Elastomeric Substrates

Abstract

Performance capabilities in traditional microelectronics are measured mainly in terms of speed, power efficiency, and level of integration. Progress in other, more recent, forms of electronics is driven instead by the ability to achieve integration on unconventional substrates (e.g., low-cost plastics, foils, paper) or to cover large areas. [1,2] For example, new forms of X-ray medical diagnosis might be achieved with large-area imagers that can conformally wrap around the body and digitally image the desired tissue.[3] Lightweight, wall-size displays or sensors that can be deployed onto a variety of surfaces and surface shapes might provide new technologies for architectural design. Various materials including small organic molecules, [4][5][6][7][8] polymers, [9] amorphous silicon, [10][11][12] polycrystalline silicon, [13][14][15][16] single crystalline silicon nanowires, [17,18] and microstructured ribbons [19][20][21][22] have been explored to serve as semiconductor channels for the type of thin-film electronics that might support these and other applications. These materials enable transistors with mobilities that span a wide range (from 10 -5 to 500 cm 2 V -1 s -1 ), and in mechanically bendable thin-film formats on flexible substrates. Applications with demanding high-speed operations, such as large-aperture interferometric synthetic aperture radar (InSAR) and radio frequency (RF) surveillance systems, require semiconductors with much higher mobilities, such as GaAs or InP. The fragility of single crystalline compound semiconductors creates a number of fabrication challenges that must be overcome in order to fabricate high-speed, flexible transistors with them. We recently established a practical approach to build metal semiconductor field-effect transistors (MESFETs) on plastic substrates by using printed GaAs wire arrays created from high-quality bulk wafers. [23,24] These devices exhibit excellent mechanical flexibility and unity current gain frequencies (f T ) that approach 2 GHz, even in moderately scaled devices (e.g., micrometer gate lengths). The work described in this article demonstrates GaAs ribbon based MESFETs (as opposed to our previously reported wire devices) designed with special geometries that provide not only bendability, but mechanical stretchability to levels of strain (strain ranges of > 20 %) that significantly exceed the intrinsic yield points of GaAs itself (ca. 2 %). The resulting type of stretchable, high-performance electronic systems can provide extremely high levels of bendability and the capacity to integrate conformally with curvilinear surfaces. The work that we report on this GaAs system extends our recently described "wavy" silicon [25] in four important ways: i) it demonstrates stretchability in GaAs, a material that is in practical terms much more mechanically fragile than Si; ii) it introduces a new "buckled" geometry that can be used for stretchability together with or independently of the previously described "wavy" configuration; iii) it achieves a new class of s...

Stretch-induced wrinkles in reinforced membranes: From out-of-plane to in-plane structures

“…In flexible electronics systems, rigid circuits are also deposited on (or embedded into) elastomeric substrates. Fine controls of the buckling and the possible delamination of the circuit occuring when the matrix is deformed are then required [11][12][13][14][15]. While the formation of wrinkles on thick soft substrates entirely covered with an inextensible thin film has been extensively studied [10,16], less works have been devoted to localized reinforcement of soft membranes by strips or fibers [17][18][19][20][21][22], although these geometries are important for applications in stretchable electronics [11,23].…”

Nanostructures induced light harvesting enhancement in organic photovoltaics

“…A range of self-assembled nanostructures induced on the surface of elastomeric polymer films by the stress relief of thin films under internal compressive stress, which have been used in biological, mechanical and physical fields including optical and electronic devices [64][65][66][67]. Figure 5 shows the schematic illustration of the fabrication of self-assembled nanostructures with the thermal annealing process.…”

Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes

“…12 While carbon based electrodes are relatively cheap and easy to fabricate, they have inherently high electrical resistivity and are often grainy and inconsistent at thinner layer thicknesses. In contrast, thin film metallic electrodes are highly conductive and easily patterned, but add to the stiffness of the DEA and require clever fabrication to undergo stretching (e.g., pre-buckling and wavy electronics 16 ).…”