Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 40: Impurities / Amorphous Semiconductors

HL 40.5: Talk

Tuesday, March 27, 2012, 12:30–12:45, EW 015

Charge Carrier Density Control in In-based Multi Compound Solution Processed Oxide TFTs — •Marlis Ortel, Marko Marinkovic, Gesa Helms, and Veit Wagner — Jacobs University Bremen, School of Engineering and Science, Campus Ring 8, 28759 Bremen, Germany

Novel oxide semiconductors have recently caught much attention for TFTs in high-end 3D-TVs and smart-sensor applications. Materials like In-Ga-Zn-O (IGZO) show very high mobility, transparency and they are solution processable. When electrical stress is applied the TFT characteristics shifts. A reason for this instability are oxygen vacancies, which are attributed to weak indium-oxygen bonds. The vacancies result in traps and doping of the active layer.

In this work charge carrier control in TFTs by addition of Al and Si to indium oxide was investigated. These components were chosen with respect to the bonding properties to oxygen. Si and Al show almost the same ionic radius but differ in the bond dissociation energy to oxygen by a factor of 1.6. A systematic influnce on the charge carrier density caused by oxygen vacancies is expected. For the investigation TFTs were electrically and morphologically characterized. The analysis gave a high mobility of 12cm2/Vs for the In-Al-O material system. The density of deep trap states near the mid-gap was analyzed to be 6.8E12eV-1cm-2 in In-Al-O and as low as 2.2E12 eV-1cm-2 in the In-Si-O material system.

In conclusion addition of silicon is a proper method to control the bulk charge carrier density, i. e. doping level, in In-based oxide TFTs.