Optimization of reactive ion beam sputtered Ta₂O₅ for III–V compounds

Abstract

<p>We report the optimization of the process parameters used in ion beam sputtering of dielectric Ta<sub>2</sub>O<sub>5</sub> thin films on III–V semiconductor surfaces, with an aim of minimizing the deterioration of semiconductor surfaces and their opto-electric performance. We demonstrate that linear tuning of the three main sputtering parameters, namely, the primary source radiofrequency power, the ion beam current, and the ion beam voltage, allows optimizing the deposition conditions of Ta<sub>2</sub>O<sub>5</sub> minimizing the damage to the III–V surfaces. The effect of parametrization is evaluated by deposition of a Ta<sub>2</sub>O<sub>5</sub> antireflection coating on GaAs-based multijunction solar cells employing AlGaAs and AlInP window layers. Numerical study reveals that the main source of damage is the scattered primary ions, in this case argon ions, that have not contributed to the sputtering process of the Ta<sub>2</sub>O<sub>5</sub> at the target. Moreover, it is likely that the reactive oxygen atmosphere oxidizes the semiconductor surfaces in the initial phase of the deposition process. A similar optimization procedure should be employed for any other thin film directly deposited by reactive ion beam sputtering on III–V surfaces and optoelectronics devices to avoid deposition induced damage.</p>