Electrical and optical properties of ZnO films prepared by sputtering of ZnO targets containing AlN

ZnO films prepared from the ZnO target containing 2% AlN are transparent irrespective of radio frequency (RF) power. The obtained ZnO films have the carrier density of 3.8 1020 cm 3 or less and the low mobility of 5.3–7.8 cm2/(V s). In the case of 5% AlN target, ZnO films prepared at 40, 60 and 80 Ware transparent, whereas ZnO films prepared at 100 and 120 Ware colored. As RF power increases from 40 to 120 W, the carrier density increases straightforwardly up to 5.5 1020 cm 3 at 100 Wand is oppositely reduced to 3.2 1020 cm 3 at 120 W. In the case of 10% AlN target, ZnO films prepared at 60 Wor more are colored, and have the carrier density of 4 1020 cm 3 or less. The N-concentration in these colored films is estimated to be 1% or less. The Al-concentration in the ZnO films prepared from the 5 and 10% AlN targets is higher than 2%. The carrier density of the ZnO films containing Al and N atoms is nearly equal to that of ZnO films doped with Al atoms alone. There is no evidence in supporting the enhancement of the carrier density via the formation of N-AlxZn4 x clusters (4 x 2).