microLED, also known as micro-LED, mLED or µLED, is an emerging flat panel display technology. As the name implies, microLED displays consist of arrays of microscopic LEDs forming the individual pixel elements. When compared to the widespread LCD technology, microLED displays offer better contrast, response times, and energy efficiency.
Along with OLEDs, microLEDs are primarily aimed at small, low-energy devices such as smartwatches and smartphones. OLED and microLED both offer greatly reduced energy requirements compared to conventional LCD systems. Unlike OLED, microLED is based on conventional GaN LED technology, which offers far higher total brightness than OLED produces, as much as 30 times, as well as higher efficiency in terms of lux/W.
As of 2018[update], microLED displays have not been mass-produced or commercialized, though Samsung demonstrated a prototype at CES and Apple has begun in-house development of microLED screens of its own.
Inorganic semiconductor microLED (µLED) technology was first invented in 2000 by the research group of Hongxing Jiang and Jingyu Lin of Texas Tech University while they were at Kansas State University. Following their first report of electrical injection microLEDs based on Indium gallium nitride (InGaN) semiconductors, several groups have quickly engaged in pursuing this concept. Many related potential applications have been identified. Various on-chip connection schemes of microLED pixel arrays have been employed allowing for the development of single-chip high voltage DC/AC-LEDs to address the compatibility issue between the high voltage electrical infrastructure and low voltage operation nature of LEDs and high brightness self-emissive microdisplays.
Early InGaN based microLED arrays and microdisplays were primarily passively driven. The first actively driven video-capable self-emissive InGaN microLED microdisplay in VGA format (640 x 480 pixels, each 12 microns in size with 15 microns between them) possessing low voltage requirements was realized in 2011 via a hybrid complementary metal-oxide semiconductor (CMOS) and integrated circuit (IC) hybrid assembly.
microLEDs are considered to have innate potential performance advantages over LCD displays, including lower latency, higher contrast ratio, and greater color saturation, plus intrinsic self-illumination and better efficiency. As of 2016, technological and production barriers have prevented commercialization.
As of 2016 a number of different technologies were under active research for the assembling of individual (pixel, or pixel group) LEDs on a substrate. These include chip bonding of microLED chips onto a substrate, considered to have potential for large displays; wafer production methods using etching to produce an LED array followed by bonding to an IC ; and wafer production methods using an intermediate temporary thin film to transfer the LED array to a substrate.
Sony launched a 55inch "Crystal LED Display" in 2012 with 1920x1080 resolution, as a demonstrator product. Sony announced its CLEDIS (Crystal LED Integrated Structure) brand which used surface mounted LEDs for large display production. Sony has become interested in developing MicroLED TVs. Samsung plans on bringing a 4K microLED TV to market in 2018. In March 2018, Bloomberg reported Apple to have about 300 engineers devoted to in-house development of microLED screens.
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