Effect of single Al2O3 cycle insertion with various positions in SnO2 thin films using atomic layer deposition

We used atomic layer deposition (ALD) to evaluate the effect of single Al2O3 cycle insertion at various locations on SnO2 and Al-doped SnO2 thin film transistors (TFTs). The ALD process was used to deposit the SnO2 thin film in 67 cycles (5 nm thickness). The position of the Al doped layer of Al-doped SnO2 was controlled by inserting a single Al2O3 cycle into the 56th, 34th and 12th cycles out of 67 cycles. The inserted Al doping layer was analyzed by secondary ion mass spectrometry (SIMS). Crystallinity and thickness of SnO2 and Al-doped SnO2 were measured using transmission electron microscope (TEM). Al-doped SnO2 thin films were prepared at different single Al2O3 cyclic positions for use as channel layers. XPS analysis showed that the oxygen vacancies within the film ranged from 32.8% to 41.6%. Also, the carrier concentration varied from 1.44 x 1016 to 2.80 x 1020 cm−3 depending on the Al doping position based on Hall measurements. In addition, the field effect mobility and on/off current ratios ranged from 1.4 to 8.1 cm2/Vsec and from 5.29 x 102 to 1.56 x 107, respectively. Lastly, the threshold voltage varied from −6.56 to 11.60 V. Overall, SnO2 and Al doped SnO2 channel layers deposited using atomic layer deposition were adjusted to exhibit switching characteristics by inserting a single Al2O3 cycle based on position.