In contrast to other III-V materials such as gallium arsenide, it is difficult to dry-etch indium phosphide at temperatures below which most photoresists will deform. Argon ion beams usually sputter phosphorus preferentially, and the common reactive dry etchants which contain fluorine and chlorine produce indium halides which are not volatile unless heated to over 150°. This paper presents some dry-etching techniques for unheated samples which may be used to overcome the above problems. Ion-beam etching at large incident angles and ion-beam assisted etching using iodine vapour are discussed in detail. These processes are investigated by various analytical techniques with respect to aspects which are important for integrated optoelectronics, namely surface composition, crystal damage, smoothness and anisotropy.
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