Comparative study of sputter‐deposited SnO₂ films doped with antimony or tantalum

Abstract

SnO2 films doped with antimony or tantalum were sputter‐deposited for comparison, using an identical set of parameters. The influence of dopant concentration and choice of deposition parameters such as substrate temperature on the optoelectronic properties, especially film resistivity, were determined. Comparative analysis shows that tantalum doping yields lower film resistivity, probably due to an increased inhibiting influence of grain boundary scattering in the case of antimony doping. Sputter‐deposited tantalum‐doped films with lower than previously achieved resistivity 5.4×10−4 Ω normalcm, carrier density 4.5×1020 cm−3, and mobility 25.7cm2thinmathspaceVs−1 are reported, while maintaining optical transmittance above 85% at a film thickness 400 nm. Ta/Sb co‐doped thin films were synthesized for the first time, achieving similar results. Comparison of resistivity values achievable by doping sputter‐deposited tin oxide films with antimony (blue) or tantalum (red) as a function of dopant concentration.

Defect Modulation Doping

“…While the obtained carrier concentrations and mobilities do not per se prove that the material has been doped beyond the values achievable by substitutional doping, it has to be kept in mind that the measurement provides a value averaged across the film thickness and therefore must by nature severely underestimate the charge carrier density in the 2DEG at the interface.…”

“…This is higher than what can be achieved by conventional doping. The modulation doping is enabled by the low processing temperature of the ALD process, which prevents the formation of compensating defects, as it is the case for the high temperatures required for obtaining high conductivities of substitutionally doped films . In the case of SnO 2 , compensating defects are not expected to prevent the modulation doping, as interstitial sites are all occupied in the rutile structure and Sn vacancies would be highly charged …”

SnO2 Films Deposited by Ultrasonic Spray Pyrolysis: Influence of Al Incorporation on the Properties

“…Doped SnO2 thin films are also used as front electrodes in optoelectronic devices such as thin film solar cells, displays and light emitting diodes [18]. In this field of application, tin oxide is an alternative to other transparent conductive oxide (TCO) materials such as Sn-doped In2O3 (ITO) [19] and Al-doped ZnO [20]. Although higher conductivity have been achieved with the two latter oxides, SnO2 based TCO materials offer enhanced chemical, mechanical, and thermal stability, as well as the relative abundance of tin ores in the earth’s crust [1].…”

“…A wide variety of growth methods can typically be used for the deposition of undoped and differently doped tin oxide thin films, including magnetron sputtering [20,21,22,23], molecular beam epitaxy [24], pulsed-laser deposition (PLD) [25], chemical vapor deposition (CVD) [26], atomic layer deposition (ALD) [27], or spray pyrolysis [28,29,30]. Spray pyrolysis has the advantages of being cost efficient and surface scalable [31].…”

Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas

“…The isotropy of their conduction bands, different from other semiconductors, like silicon or GaAs, is advantageous for the good transport properties (high carrier mobility) of these transparent conductive oxides even in the amorphous state [1,2]. and tantalum in SnO 2 films deposited by magnetron sputtering [34]. They achieved a significantly lower resistivity of SnO 2 :Ta (5.4 × 10 −4 Ωcm) compared to SnO 2 :Sb films by a factor of 3.…”