Oxygen Sensitivity in Gallium Oxide Thin Films and Single Crystals at High Temperatures

Abstract

In this paper, the oxygen sensitivity of gallium oxide thin films and single crystals at high temperatures is presented. To investigate the oxygen sensing mechanism at high temperature, we used sputtered β-Ga2O3 thin films and β-Ga2O3 single crystals with different electrode geometries. For β-Ga2O3 single crystals: a response time of about 10 s was achieved, while for β-Ga2O3 thin-film this was about 11 s. For single crystal samples the response time does not depend on the type of electrode. This can be explained by the combination of a greater influence of surface effects and smaller influence of bulk effects.

ALD and MOCVD of Ga2O3 Thin Films Using the New Ga Precursor Dimethylgallium Isopropoxide, Me2GaOiPr

“…[36] Ga-doped zinc oxide (ZnO:Ga, GZO) is a wellknown n-type TCO material. [37] Thin films of gallium oxide have been prepared by various methods: (radiofrequency) magnetron sputter deposition, [1][2][3][4]6,7,9,10,12,25,27] electron beam evaporation, [15][16][17]21] pulsed laser deposition, [26,28,30,33,34,36] laser ablation, [31] CVD, [38][39][40][41][42][43][44][45][46][47] ALD, [48][49][50][51][52] molecular beam epitaxy, [32,35] vapor phase epitaxy, [53] spray pyrolysis, [54,55] and sol-gel process. [5,13,23,24] Among these methods, CVD is considered very important because it can readily be employed in industrial processes.…”

Mechanism of oxygen sensing on β‐Ga2O3 single‐crystal sensors for high temperatures

“…As can be seen, all three sensor types had the same trend of the sensitivity in air: increasing to a maximum around 800 °C, then decreasing drastically and finally, going to a plateau. On the other hand, at lower temperatures (up to 900 °C) the value of the sensitivities varies with the electrode types, probably because of the limit process depending on (i) reaction, thus, as the exposure surface was larger the sensitivity was higher while when the electrodes were bigger the sensor surface contact with the testing gas was smaller and the sensitivity decreased As shown in our previous work , on increasing the working temperature, over 900 °C, the sensor performances were independent of the electrode shape and it might be concluded that the rate‐limiting step could be the process (ii) at that temperature. However, as mentioned above, at temperatures below approximately 800 °C the conduction of the sensor could be partly associated with hydrogen removal , while the resistivity saturation above 900 °C, as seen in Fig.…”

“…At high temperatures, the oxygen-sensing properties of Ga 2 O 3 sensors were studied on either polycrystalline thin films obtained in various conditions [16][17][18][19][20] or on single crystals [21]. Summarizing the results from the literature obtained at 1000 8C, it can be concluded that the b-Ga 2 O 3 thin-film sensors having various electrode geometries showed a sensitivity of $1.50 depending on the film deposition conditions [16][17][18][19][20] and response times of about 15-25 s. On the other hand, at the same high temperature using b-Ga 2 O 3 single-crystal, sensors responded to oxygen gas in 11 s, but the sensitivity was quite low, reaching only a value of 1.06 [21].…”

Improvements of electronic and optical characteristics of n-GaN-based structures by photoelectrochemical oxidation in glycol solution

“…17,18 Crystalline gallium oxide ͑␤-Ga 2 O 3 ͒ itself is also an attractive material for sensing various gases and as a transparent conductive oxide. [19][20][21] For further practical use of wet oxidation and gallium oxide, it is essential to understand fundamental information about such oxidation and oxides. It is unlikely that the same etching properties given in primary reports can necessarily be obtained because of recent improvements in the crystalline quality of GaN epitaxial layers, including decrease in the residual carrier density.…”