Comparisons of Gallium Nitride and Indium Nitride Properties after CF 4 / Argon Reactive Ion Etching
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Comparisons of Gallium Nitride and Indium Nitride Properties after CF4 / Argon Reactive Ion Etching
Marie WINTREBERT-FOUQUET, K. Scott A. BUTCHER, Physics Department, Macquarie University, Sydney NSW 2109, Australia and Simon K H Lam, CSIRO Telecommunications & Industrial Physics, PO Box 218, Lindfield, NSW 2070, Australia
ABSTRACT We present a comparative study of the effects of low power reactive ion etching (RIE) on GaN and InN. This new, highly chemical, dry etching, using CF4 and Ar, has been developed for thin nitride films grown at low temperature in our laboratories. GaN films were grown by remote plasma enhanced-laser induced chemical vapor deposition and InN films were grown by radiofrequency RF reactive sputtering. Commercial GaN samples were also examined. Optical and electrical characteristics of the films are reported before and after removing 100 to 200 nm of the film surface by RIE. We have previously shown that the GaN films, although polycrystalline after growth, may be re-crystallized below the growth temperature. Removal of the surface oxide has been found to be imperative since a polycrystalline residue remains on the surface after recrystallization.
INTRODUCTION III-V nitrides have some unique properties, such as wide band gap, high thermal conductivity and chemical stability, which make them ideal materials for optoelectronic and high power devices. III-V nitrides have high bond energies compared to conventional III-V semiconductors and are therefore more difficult to process for device applications. Dry etching of nitrides has been extensively investigated using numerous plasma-based machines and sources[1]. However, only a few studies on etching damage have been published. A large number of high-density plasma dry etch processes have been developed to obtain vertical and smooth sidewall profiles for nitride optoelectronics devices[2]. In addition to etch anisotropy, an important consideration for device fabrication is the elimination of ion damage. Achieving high anisotropy generally requires high, ion assisted etch rates. In this work we report on the RIE of our thin nitride films performed using CF4/Ar chemistries. These thin GaN and InN films are grown in our lab at low temperature. We investigate the effect of the rf plasma power as a function of etch rate and surface contamination. We also present the results of an investigation into the cause of etch-induced damage for this chemistry. The GaN and InN films exposed to RIE were examined electrically, chemically and optically to identify the effects of various treatments.
EXPERIMENTAL DETAILS GaN films were grown by remote plasma enhanced-laser induced chemical vapor deposition at 550-600 °C on Si (100) and Sapphire substrates. Although the GaN was polycrystalline after growth, it may be re-crystallized below the growth temperature[3]. InN films were grown by radio-frequency reactive sputtering at 80 °C on borosilicate glass, sapphire and Si(100) substrates.
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The RIE was performed in a conventional RF-power reactor.
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