~iiiiiiii~iiiiiiiiittiiiiii~iti~i!iiii~iiiiiitii~itititii!ii!iii surface science ELSEVIER Applied Surface Science 93 (1996) 119-130 Plasma anodic oxidation of semiinsulating GaAs Emil Pin6ik a,*, Katarina Gmucovfi a, Jill Barto~ a, Michal Ku6era b, Matej Jergel a, Robert Brunner a a Institute of Physics, Slo~'akAcademy of Sciences, Dubravska cesta 9, 842 28 Bratislava, SIovak Republic b Institute of Electrical Engineering, Slovak Academy of Sciences, Dubrat,ska cesta 9, 842 39 Bratislava, Slovak Republic Received 17 July 1995; accepted for publication l0 September 1995 Abstract A technique is presented for the plasma anodic oxidation of semiinsulating (SI) GaAs surfaces at elevated sample temperatures (up to 230°C) the anodization current being fed vertically across the semiconductor. Capacitance and resistance measurements were performed on corresponding MOS structures for the determination of the lowest temperature at which the oxide growth can proceed. The oxide/SI-GaAs interface properties were investigated by correlation of DLTS, photoluminescence and X-ray reflectivity methods with the aim to better clarify the oxidation kinetics. Moreover, it was determined that the interface region seems to be better formed, being thinner, when a thin aluminium coverage layer is deposited on the SI-GaAs surface before the oxidation process. On the basis of our experimental results, we presume that each anodic oxidation process can be characterized by a cross section of the reaction of the oxygen ions with the semiconductor atoms due to the different oxidation state of the latter which is determined by given oxidation conditions. Its value for SI-GaAs sample at 230°C has been calculated to be ~ 3.0 x l0 14 cm 2. 1. Introduction The possibility of an oxide film formation at low temperatures during the plasma anodic oxidation of semiconductors is an important advantage which can be utilized for microelectronic applications. It has been concluded [1-4] that, in this technique, the density of the negatively charged oxygen species rising in the oxygen plasma and/or at the oxidized Corresponding author. Tel.: +42-7372479; fax: +42- 7376085. surface influences the oxide growth rate. From the other important parameters determining the growth process of the oxide layer the following should be enumerated: the temperature of the sample, the inten- sity of the applied electric field, the atomic composi- tion of the sample. The oxidation behaviour may be different for a one-component sample (Si, metal) and compound (ZrSi 2, GaAs), in the latter case the be- haviour being more complex. Perriere et al. [5] stated on the basis of "marker" and "tracer" experiments that the oxidation of ZrSi 2 proceeded under low-field conditions (T = 300°C, E = 6 x 106 V cm ]) by the place-exchange mechanism which can be viewed as 0169-4332/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0169-4332(95)00320-7