Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Focus Session: Crystalline n-type semiconducting oxides - SnO₂, Ga₂O₃, and In₂O₃ for novel devices (jointly with HL)

O 13.7: Vortrag

Montag, 11. März 2013, 17:30–17:45, H2

Schottky contacts on β-Ga₂O₃ thin films grown by pulsed laser deposition — •Daniel Splith, Stefan Müller, Holger von Wenckstern, and Marius Grundmann — Universität Leipzig, Semiconductor Physics Group, Institut für Experimentelle Physik II, Leipzig, Germany

A promising oxide semiconductor for high power electronics and transparent optoelectronic devices is β-gallium oxide (Ga₂O₃) with a band gap of about 4.9 eV. We have investigated the preparation and the properties of Schottky contacts (SCs) on Ga₂O₃ thin films. The thin films were grown from a Ga₂O₃ target with 1% SiO₂ on c-sapphire substrates using pulsed-laser deposition at an oxygen pressure of 10⁻³ mbar. The ohmic contacts were fabricated by thermal evaporation of Ti and Al as reported in [1]. Subsequently, we prepared SCs by normal and reactive DC sputtering of metals like Nb, W or Cu. The I−V characteristics of such SCs showed rectification ratios up to 8 orders of magnitude for some of the Nb contacts. The dominant current transport mechanism is thermionic emission. From fits we determined ideality factors n down to 1.15 for the best W contacts and barrier heights Φ_B up to 1.2  eV for the best Cu contacts. Temperature dependent I−V measurements yielded a linear dependence of Φ_B and 1/n−1 on the inverse temperature in accordance to the theory of thermionic emission in the presence of a laterally inhomogeneous barrier. E. g. the mean barrier height Φ_B for the Cu contacts is determined to be 1.6 eV with a standard deviation σ_Φ of 0.17 eV.

[1] E. G. Villora et al., Appl. Phys. Lett. 92, 202118 (2008)