Reinventing Displays with AMNRs

Amorphyx AMNR Technology

Thin-film transistors (TFTs) replaced thin-film diodes (TFDs) as the active device in display backplanes in the late 1990s as the LCD moved from seven-segment alphanumeric applications to high-resolution monitors, laptops and televisions.  By 2003 the LCD replaced the CRT as the largest-volume TV display technology.  As TVs - and later laptops, smartphones, monitors and tablets - began a path of increasing resolution through "1080p" or "full HD" and currently to "Ultra HD", the demands on TFT performance and manufacturing yield moved beyond the limitations of the amorphous silicon-based TFT that has been the backbone of the LCD industry for more than a decade.

The a-Si TFT's relatively poor electron mobility - a measure of the ability of a semiconductor material to conduct electrical current - combines with the sensitivity of the device's performance to light and heat to make it unsuitable for the current and future generations of display backplanes.  Improvements in TFT performance through laser annealing the amorphous silicon after vapor deposition onto display glass (called "low temperature polysilicon", or LTPS) to date have created needed improvements in backplane performance for LCD and OLED displays, but also have resulted in significantly higher manufacturing costs for backplanes.  New developments in amorphous compound semiconductors for TFTs - primarily indium gallium zinc oxide (IGZO) - achieve LTPS-like performance at cost levels below LTPS.  However, In a TV display industry generating over $10 billion in annual operating losses, a breakthrough in the cost and simplicity of backplane manufacturing is needed to return the display industry to profitability.

Now, thanks to Amorphyx, the display industry can stop investing billions of dollars in the hope of someday creating a TFT device and manufacturing process that delivers the performance needed for high-resolution LCDs at cost levels that once again support profitabilty from retail TV sales.

Amorphyx discovered that the improved performance of amorphous metal-based nonlinear resistors (AMNRs) enables the replacement of TFTs as backplane devices that act as the "dimmer switches" that control the brightness of each pixel in a display.  An amorphous metal (also known as "metallic glass" or "glassy metal") is a solid metallic material comprised of two or more elemental components, with a disordered atomic-scale structure.  Amorphous silicon TFTs are produced using silicon that has been vaporized for deposition onto glass in a way that eliminates the crystalline structure of the silicon.  Most metals are crystalline in their solid state, but amorphous metals are non-crystalline, actually glass with good electrical conductivity.  In the diagram below, you see the surface structural difference of an amorphous metal and a crystalline metal.



An AMNR-LCD backplane is fabricated using the same processing equipment as a TFT backplane, but requires significantly fewer processing steps because the AMNR is a simpler, two-terminal device constructed of three thin films instead of the 5-9 thin films used in three-terminal a-SI and IGZO TFTs. This ultimately saves time, boosts production efficiency, and reduces material consumption - all contributing to a reduction in cost and an increased bottom line.

The AMNR acts as the dimmer switch, analogous to the semiconductor TFT,  to control the brightness of each pixel. But unlike TFTs, Amorphyx’ AMNRs have no light sensitivity and have low temperature sensitivity.  These qualities add to the simplification of the LCD module over TFT-based modules.  Simplification leads to lower manufacturing costs. 

Semiconductor-based electronic devices such as TFTs operate on the principle of ohmic conduction - the use of an intermediate material as a conductor to move electrons through the device.  The AMNR operates on the principle of Fowler-Nordheim current tunneling, where electrons are transported through an intermediate material while not interacting with it.  While Fowler-Nordheim tunneling sounds more like science fiction than a viable mode of operation for an electronic device, the Amorphyx AMNR is not the first instance of Fowler-Nordheim tunneling in an electronic device.  All solid state data storage devices are based on "flash" memory, which stores data using field-effect transistors operating on Fowler-Nordheim principles.  From USB memory sticks to solid-state hard drives in computers and tablets, Fowler-Nordheim tunneling is a mechanism for electronic device operation that has been validated with over a decade of mass production.

Flexibility is also inherent to amorphous metals, offering manufacturers the potential to explore more innovation with flexible displays and even consider roll-to-roll display manufacturing.  Flexible displays are rapidly gaining in popularity for consumer devices - and flexible backplanes offer the promise of a signifcant cost reduction to existing LCD modules.  Through its flexible thin films and its significantly thinner profile relative to TFTs, the AMNR is an intriguing option to TFT technologies that will help bring flexible displays to market.