High mobility n-type Zn3N2 thin films as channel for thin film transistors

C. García Núñez, J.L. Pau, E. Ruíz, M.J. Hernández, M. Cervera, J. Piqueras

Research output: Contribution to conferencePaper

Abstract

Thin film transistors (TFTs) are essential devices in active-matrix liquid crystal and organic light-emitting diode displays. Although hydrogenated amorphous silicon is usually the material of choice for the TFT channel, this technology presents some issues such as low mobility or poor stability. Zinc nitride (Zn3N2), is a II-V compound recognized as potential substitute of Si due to its high mobility, and conductivity as well as its low-cost and low-temperature processing. This work aims to characterize Zn3N2 properties as a function of the deposition parameters in layers grown on different substrates and TFT fabrication procedure in order to optimize the output characteristics of those devices.

Zn3N2 films were grown by radio-frequency magnetron sputtering in Ar/N2 ambient using Zn target (99.995%) on glass and Si(100) substrates. The incorporation of impurities (especially O) in the nitride layers during and after the sputtering growth was analyzed by a combination of different ion beam analysis techniques, spectroscopic ellipsometry and transmission spectroscopy [1].

Electrical properties such as resistivity, electron concentration and mobility were determined by Hall-effect measurements using the four-probe Van der Pauw technique. Through the optimization of the growth conditions [2], a maximum mobility of 99 cm2/Vs was reached for an electron concentration of 3.2x1018 cm-3 at a 423-K growth temperature, 4.4-nm/min growth rate, and 73%-rich N2 ambient.

Based on these studies, TFTs were fabricated using bottom- and top-gate configurations on Si(100) and glass substrates, respectively. Drain, source and gate electrodes consisted of a 100-nm thick Al layer were patterned by optical lithography and lift-off. A 200-nm thick SiO2 layer was chosen as a gate oxide. Zn3N2 channels were deposited with thicknesses ranged between 100-500 nm and a thin ZnO cap layer atop of it aiming to prevent Zn3N2 oxidation. Different channel lengths ranged between 2-20 µm were studied keeping constant a channel width of 180 μm. Those devices showed characteristic ID-VDS transistor curves sensitive to visible light exposure.
Original languageEnglish
Pages11-12
Number of pages2
Publication statusPublished - 15 Dec 2011
Externally publishedYes
EventXIV Jornada De Jóvenes Científicos Del Instituto De Ciencia De Materiales Nicolás Cabrera - Madrid, Spain
Duration: 15 Dec 2011 → …

Conference

ConferenceXIV Jornada De Jóvenes Científicos Del Instituto De Ciencia De Materiales Nicolás Cabrera
CountrySpain
CityMadrid
Period15/12/11 → …

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Núñez, C. G., Pau, J. L., Ruíz, E., Hernández, M. J., Cervera, M., & Piqueras, J. (2011). High mobility n-type Zn3N2 thin films as channel for thin film transistors. 11-12. Paper presented at XIV Jornada De Jóvenes Científicos Del Instituto De Ciencia De Materiales Nicolás Cabrera , Madrid, Spain.