Influence of Aluminium Incorporation on the Semiconducting Properties of P-type Tin Monoxide

Herein, we report the first TFTs using Sn(HMDS)2 as a precursor for the atomic layer deposition of SnO. We subsequently, investigate the incorporation of Al-ions in the device channel, from three aluminium sources using low energy ion scattering. Alumina is widely exploited in the fabrication of p-type tin monoxide (SnO) thin film transistors. It has been used as a surface passivation, as a dopant, and as a substrate barrier layer. Alumina is a source of Al3+, which is a compensating donor in SnO. We demonstrate that the intentional incorporation of aluminium into SnO, by introducing alumina cycles during atomic layer deposition, has the effect of increasing the sheet resistance of the SnO films by 105 times and amorphising the film microstructure. Further, the incorporation of Al ions from alumina passivation-capping and barrier layers is revealed at their interfaces with the SnO TFT channel. The transfer characteristics of thin film transistors fabricated from the Al-doped and capped SnO films is used to show the effects of annealing, which are explained in terms of Al ion incorporation. Interdiffusion or incorporation of Al ions, into the SnO semiconductor, identified by depth profile low energy ion scattering, indicates that auto-doping plays a significant role in modifying the characteristics of SnO TFTs. The application of alumina layers in the design of p-type tin monoxide thin film transistors must take account of the influence of Al ion incorporation on the semiconducting properties of SnO.