Breakthrough TFT material for LCD and OLED displays
Solar-Tectic and Blue Wave Semiconductors have announced that a breakthrough material for dramatically improving the performance of thin-film transistors (TFTs) used in almost all displays on the market, such as LCD, LED and OLED, has been patented by the USPTO.
Specifically, the patent (U.S. No. 9,856,578) is for making crystalline films on glass at low temperature with a high degree of crystal orientation or "texture".
The particular material demonstrated, which has been reported on in a scientific journal(http://www.sciencedirect.com/science/article/pii/S0167577X14001451), is Magnesium Oxide (MgO). The insulating material is not only highly transparent, but also has very high thermal conductivity, high thermal stability, and a high melting point. Perhaps most importantly, however, the new material has an unusual (111) orientation which can enhance the preferred orientations of silicon and germanium.
Silicon is used in almost all TFTs made today in a process called LTPS (low temperature polysilicon) and the new MgO material promises greatly to enhance the LTPS process (as well as common a-Si TFT process) because of its high (111) texture which, by inducing texture in the silicon without chemical degradation, can greatly increase electron mobility. This is due to the resulting aligned crystals along the c-axis. The electrical performance and homogeneity of semiconductor layers can also be enhanced by the highly crystalline and oriented MgO film.
The thin-film can be grown in a wide range of thicknesses, and deposited on a variety of technical glasses, including soda-lime or alkali-free glass, at temperatures as low as ~450°C or lower. The MgO film, when deposited on soda-lime glass, serves as a diffusion barrier preventing impurities such as Na from contaminating the silicon layer along with enhancing the crystallography along the (111) plane.
