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TRANSIENT ANNEALING OF ION IMPLANTED GALLIUM ARSENIDE J.S. WILLIAMS JMRC, Faculty of Engineering, Royal Melbourne Institute of Technology, Melbourne 3000, Australia. ABSTRACT

This paper provides a brief overview of the application of transient annealing to the removal of ion implantation damage and dopant activation in GaAs. It is shown that both the liquid phase and solid phase annealing processes are more complex in GaAs than those observed in Si. Particular attention is given to observations of damage removal, surface dissociation, dopant redistribution, solubility and the electrical properties of GaAs. The various annealing mechanisms are discussed and areas in need of further investigation are identified. INTRODUCTION Over the past few years, considerable attention has been given to transient annealing of ion implanted semiconductors. Most of the important results of this research effort have been reported or reviewed at the previous symposia in this series and appear in the corresponding proceedings [1 - 4]. Annealing has been carried out in time regimes which span 18 orders of magnitude, using,for example, picosecond laser pulses to rapidly melt and refreeze near-surface layers at one end of the time spectrum, to the utilization of solid phase annealing via more conventional furnace processing at the other end of the time scale. Although considerably more effort has been directed towards Si, transient annealing has much intuitive appeal for thermal processing of GaAs.

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example, major difficulties are experienced using furnace processing; namely, in removing implantation damage, low activation of n-type dopants and the necessity of protecting the surface against dissociation and As loss. However, the initial hope that transient processing might overcome such difficulties has, to a large extent, not been realised in practice. As outlined in previous review articles [5 - 7], the results of transient annealing of GaAs attest to the difficulties of completely removing damage and activating dopants, regardless of the annealing regime (solid or liquid phase crystallisation) or of the particular time regime employed. This brief review summarises the available results which have been obtained using transient thermal processing of ion implanted GaAs. It assesses the present understanding of the various annealing processes, both in the liquid phase and solid phase regimes, and identifies some key areas which are open for further investigation.

ANNEALING IN THE LIQUID PHASE REGIME Since existing reviews [ 7,8] provide an accurate assessment of the current status of rapid liquid phase annealing of GaAs, only a brief summary of the important points is given here. Mat. Ras. Soc.Symp. Proc. Vol. 13 (1983) QElsevier Science Publishing Co., Inc.

622 Damage removal and dissociation Figure 1 summarises the typical behaviour which results when nanosecond energy pulses of increasing energy density are incident upon ion implanted GaAs. As the energy density within a single pulse is increased a thin near-surface region wil