Patent ID: 7872259

Claim:
A light-emitting device having a light-emitting element comprising first and second electrodes and a light-emitting layer existing between the first and second electrodes, and a field effect transistor for driving the light-emitting element, wherein an active layer of the field effect transistor comprises an amorphous oxide of a compound having (a) a composition when in crystalline state represented by In 2−x M3 x O 3 (Zn 1−y M2 y O) m , wherein M2 is Mg or Ca; M3 is B, Al, Ga or Y; 0≦x≦2; 0≦y≦1; and m is zero or a natural number less than 6, or a mixture of said compounds; (b) an electric carrier concentration of greater than 10 12 /cm 3 and lesser than 10 18 /cm 3 wherein a current between a drain terminal and a source terminal of the field effect transistor when no gate voltage is applied is less than 10 microamperes, and wherein an electron mobility of the amorphous oxide increases when the electron carrier concentration increases; and (c) controlled oxygen defect density resulting from treatment in an atmosphere including oxygen at a predetermined pressure during or after formation of the active layer of the amorphous oxide.