New TFT technology could replace LTPS for OLED, LCD, and solar devices

New thin-film-transistor (TFT) technology will increase efficiency and luminance while decreasing cost.

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Solar-Tectic (ST; Briarcliff Manor, NY), with assistance from Binghamton University (Binghamton, NY) and Blue Wave Semiconductor (BWS; Baltimore, MD), has patented new thin-film-transistor (TFT) technology that will increase efficiency and luminance while decreasing cost for organic light-emitting diodes (OLEDs), active-matrix OLEDs (AMOLEDs), and liquid-crystal device (LCD) displays, as well as solar cell devices.

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Unlike conventional low-temperature polysilicon (LTPS) processes used to manufacture the TFTs that drive the pixels in a display and require expensive excimer-laser annealing, the new process is a variation of metal-induced crystallization (MIC) and uses a modified liquid-phase-epitaxy (or vapor-liquid-solid) electron-beam process at low temperature (as low as 232°C) to deposit a thin layer of metal onto a metal oxide such as a magnesium oxide (MgO) buffered substrate, after which the final vaporized silicon (Si) layer is deposited and crystallizes into an approximately 50- to 100-nm-thick film without metal residue. Using Raman and x-ray spectroscopy, analysis of the Si film revealed a very high electron mobility of 188 cm2/Vs (compared to the typical 100 cm2/Vs for LTPS). The researchers expect to improve electron mobility even further by using ST’s and BWS’s oriented MgO (111) film buffered substrates to further increase crystal size. Reference: P. P. Rajbhandari et al., Mater. Lett., 219, 138–142 (2018).

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