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...
