Stability of semiconducting gallium oxide thin films

• Published in: Thin solid films 1990-09, Vol.190 (1), p.93-102
• Main Authors: Fleischer, M., Hanrieder, W., Meixner, H.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Physics
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(90)90132-W

In bulk, gallium oxide is a semiconducting oxygen-sensitive material at temperatures of over 500 °C. With the aid of a high frequency sputter process, films could be produced with thicknesses in the micrometre range using a Ga 2O 3 ceramics target. The stoichiometry and purity of these films could be demonstrated with Rutherford backscattering spectroscopy and X-ray fluorescence. Scanning electron microscopy investigations showed that, at temperatures of over 1100 °C for 50 h, crystallites approximately 200 nm in size are formed. The d.c. conductivity of these films was measured for the first time. At high temperatures, semiconducting properties similar to those of the bulk material were demonstrated. The conductivity of the Ga 2O 3 films is dependent on the oxygen content of the surrounding atmosphere. The exponent of the σ vs. P O 2 − n curve was n⩽ 1 4 . Auger spectroscopy was used to show that, at temperatures around 1000 °C, interdiffusion of the Al 3+ and the Ga 3+ ions takes place on substrates containing aluminium, thus destroying the conductivity of the film. Therefore Al 2O 3 ceramic substrates which are standard in thick film technology are unsuitable for stable oxygen-sensitive Ga 2O 3 thin film devices. Alternatives are shown.