A Printable Form of Single‐Crystalline Gallium Nitride for Flexible Optoelectronic Systems

Abstract

Printable semiconductors have recently gained widespread attention due to the potential they engender in enabling the fabrication of revolutionary new forms of lightweight, mechanically flexible circuits. [1][2][3][4] A primary attraction of these materials resides in the fact that they can be deposited in patterned forms onto various substrates, including low-cost plastics and even paper, by using intrinsically low-cost means of fabrication. This ability, and the novel form factors of the devices they serve to enable, may lead to new opportunities in broad areas of commercial electronics technology. [5][6][7] However, the inherent properties, notably the mobilities of carriers in materials that have been explored most extensively, serve to limit the range of these applications. Small-molecule and polymeric semiconductors [8] can be used to form transistors whose mobilities typically fall in the range of 0.1-1 cm 2 V À1 s À1 . Nanowire and nanoparticle semiconductors, [9] another printable class of semiconductor material, yield devices with mobilities of % 1-3 cm 2 V À1 s À1 .Single-walled carbon nanotubes have exceptional intrinsic transport properties [10] and, in the form of networks and arrays, have been used to form devices with more promising mobilities, ranging from % 10 to 40 cm 2 V À1 s À1 . [11] Often, these nanowire-or nanotube-based devices show effective device mobilities that are too low for many classes of circuits, due primarily to the relatively low filling factor of semiconducting elements in the channel. [6] We recently described a complementary approach based on printable forms of single-crystalline inorganic semiconductors (Si, GaAs, InP), which we refer to as microstructured semiconductors (ms-SC), for these types of applications. Here, micrometer-scale elements, which have some advantages compared to the types of nanometer-scale objects explored previously, are derived by patterning and etching high-quality, wafer-scale sources of the semiconductor. [1] This "top-down" approach to printable inorganic semiconductors provides deterministic control over the resulting shapes of the objects-wires, ribbons, rectangles, etc.-and their spatial organization across the wafer. [1,2] High fill factors, and correspondingly high effective device mobilities, can be achieved readily. This attribute enables a multitude of possibilities for new applications that use device substrates (e.g., plastics, paper, etc.) which are incompatible with the high-temperature steps that are generally required to grow and subsequently process these semiconductors.Herein, we describe procedures suitable for generating and printing collections of microribbons of GaN, or ms-GaN, onto plastic substrates. [2, 12] GaN is a material that is not generally available in the form of bulk single-crystalline wafers, the preferred forms of the semiconductors used in our earlier work. To fabricate ms-GaN, we employ instead high-quality GaN thin films that are supported on sacrificial handle wafers, materials grown by using a metal-organi...

Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor

“…Dislocation-free GaN membrane has been exfoliated with limited lateral dimension. [ 5 ] There have also been efforts and demonstrations in separating µm-thick GaN device structures from substrates using laser liftoff, [ 6 ] chemical liftoff, [ 7 ] electrochemical liftoff, [ 8,9 ] and mechanical liftoff on suitable buffer layers. [ 10,11 ] These works open the way for vertical device confi guration but fall short in the pursuit of ultrathin (<500 nm), mechanically fl exural membranes.…”

Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

“…The third category of techniques are dry-transfer methods involving the relocation of semiconductor materials 16 or fully fabricated devices 17 from inorganic substrates to plastic using poly(dimethylsiloxane) (PDMS) stamps or soluble glues. Dry transfer has been used to print a variety of photolithographically defined semiconductor microwires 16,[18][19][20] onto plastic. These microstructured ribbons 21 are useful for circuits where high currents are required.…”

Piezoelectric BaTiO3Thin Film Nanogenerator on Plastic Substrates

“…The BaTiO 3 thin film was then transferred onto a flexible substrate by means of standard microfabrication and soft lithographic printing techniques. [17][18][19][20] To measure the positive and negative output voltage/current signals, we deposited the IDEs on flexible BaTiO 3 . Figure 1a shows a schematic of the fabrication steps.…”