Transient and Furnace Annealing of Ion Implanted Gallium Arsenide
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and Materials Processing
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TRANSIENT AND FURNACE ANNEALING OF ION IMPLANTED GALLIUM ARSENIDE
J. S. WILLIAMS AND H. B. HARRISON, Department of Communication and Electronic Engineering, Royal Melbourne Institute of Technology, Melbourne, 3000, Australia.
ABSTRACT This review examines the annealing behaviour of ion implanted gallium arsenide during furance, laser and e-beam processing. The two annealing regimes, namely solid phase regrowth via furnace or CW laser/e-beam annealing and liquid phase epitaxy produced by pulsed lasers/e-beam, are examined in some detail. Emphasis is placed upon an understanding of the physical processes which are important during the various annealing modes. Comparison with the annealing behaviour of ion implanted elemental semiconductors(notably silicon) is made throughout the review to highlight relevant similarities and differences between compound and elemental semiconductors. The electrical properties of annealed gallium arsenide layers are not treated in any detail, although particular observations which are relevant to the annealing processes are briefly discussed.
INTRODUCTION Transient annealing of semiconductors (using high intensity sources of both photons and electrons) has been the subject of intense interest over the past few years 11-31 since it offers an attractive alternative to conventional furnace annealing for the removal of ion implanted damage. The major thrust has been directed towards silicon, and the operative transient annealing mechanisms are now well understood. For short, nsec pulses of intense photons or electrons the near-surface melts [4] and near-perfect recrystallisation proceeds epitaxially from the liquid phase. For longer dwell time (>l msec.) scanned laser and electron beams, the near-surface can attain a sufficiently high temperature, below the melting point, for long enough to induce recrystallisation in the solid phase [5]. The latter process is essentially analogous to an ultra-rapid furnace anneal. Applications of transient annealing to compound semiconductors, and gallium arsenide in particular, have not received the degree of attention which has been devoted to silicon. This is in spite of the great difficulties which exist with conventional furnace annealing of compound semiconductors [6] and the possibilities that transient annealing would appear to offer in terms of controlling a major problem - surface decomposition. Nevertheless, considerable data now exist for transient annealing of ion implanted gallium arsenide and clear trends in the annealing behaviour have emerged. However, the understanding of the operative damage removal process is less advanced than for the anneal behaviour of silicon and the electrical properties following transient annealing are not yet as impressive as those which have been achieved with silicon. This brief review concentrates on the annealing mechanisms operative during transient and furnace annealing of ion implanted gallium arsenide. The removal of ion implant damage, implant redistribution and lattice
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