Indium gallium zinc oxide
Indium gallium zinc oxide (IGZO) is a semiconducting material, consisting of indium (In), gallium (Ga), zinc (Zn) and oxygen (O). IGZO thin-film transistor (TFT) is used in the TFT backplane of flat-panel displays (FPDs). IGZO-TFT was developed by Professor Hideo Hosono's group at Tokyo Institute of Technology and Japan Science and Technology Agency (JST) in 2003 (crystalline IGZO-TFT) and in 2004 (amorphous IGZO-TFT). IGZO-TFT has 20-50x higher electron mobility than amorphous silicon, which has often been used in liquid-crystal displays (LCDs) and e-papers. As a result, IGZO-TFT can improve the speed, resolution and size of flat-panel displays. It is thus considered to be one of the most promising thin-film transistors for use in organic light-emitting diode (OLED) displays.
In 2012, Sharp was first to start production of LCD panels incorporating IGZO-TFT. Sharp employs IGZO-TFT for smartphones, tablets, 32" LCD, etc. In these, the aperture ratio of the LCD is improved by up to 20%. Power consumption is improved by LCD idling stop technology, which is possible due to the high mobility and low off current of IGZO-TFT. Sharp has started to release high pixel-density panels for notebook applications. IGZO-TFT is also employed in the 14" 3,200x1,800 LCD of an ultrabook PC supplied by Fujitsu and a 55" OLED TV supplied by LG Electronics.
IGZO's advantage over zinc oxide is that it can be deposited as a uniform amorphous phase while retaining the high carrier mobility common to oxide semiconductors. The transistors are slightly photo-sensitive, but the effect becomes significant only in the deep violet to ultra-violet (photon energy above 3 eV) range, offering the possibility of a fully transparent transistor.