5,291-ppi OLED display enabled by monolithic integration of C-axis-aligned crystalline IGZO FET and Si CMOS

For the first time in the world, we have fabricated an organic light-emitting diode (OLED) display that monolithically integrates Si CMOS and oxide semiconductor FETs (OSFETs). OSFETs can be monolithically stacked on Si CMOS. With this OS/Si monolithic stack technology, we have fabricated driver circuits with Si CMOS and pixel circuits with OSFETs. This enables displays to have thin bezels. In addition, fabricating pixel circuits with OSFETs, which have higher breakdown voltage than Si CMOS, allows the use of tandem OLED devices that require high driving voltage. This enables an OLED display with a pixel density over 5,000 ppi.