Diffusion of Implanted Dopants and Isolation Species in III-V Nitrides
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ABSTRACT Twelve different elements used for doping or isolation were implanted into GaN, (and selected species into AIN and InN), and the resulting range parameters were measured by Secondary Ion Mass Spectrometry. For lighter elements such as Be, F and H the agreement between experimental range and range straggle dtermined using a Pearson IV computer fitting routine and those predicted by TRIM 92 calculations was good, but for heavier elements such as Ge and Se the discrepancy can be as much as a factor of two in range. There was little redistribution of any of the investigated species up to 700 °C, except for 2H in AIN and S in GaN. Elements such as F and Be which are generally rapid diffusers in III-V compounds do not display any redistribution in GaN for temperatures up to 800 'C. INTRODUCTION GaN and related compounds are enjoying renewed interest for applications ranging from short wavelength photonic devices such as blue light-emitting diodes to high temperature field effect transistors.("7) To date the only results from ion implantation of these materials has involved introducing color centers for changing the peak luminescence.(8) To fully exploit wide bandgap nitride technology it is necessary to develop ion implant doping and isolation techniques for selective area alteration of the electrical resistivity. A first step is to experimentally measure implantation ranges and range straggles and compare these to the values predicted by existing profile codes. A second key requirement is to understand the redistribution of implanted dopants and isolation species in these materials at typical processing temperatures, which for GaN is expected to be inthe range 700 to 900 0C. A similar temperature range is also appropriate for AIN, while for InN the maximum temperatue is approximately 600 *C due to extensive loss of N from the surface.(9 ) Eventually, dopant electrical activation needs to be careflully investigated. In this paper we report on the implantation ranges and straggles for the implanted dopants, (Be, Mg, Zn, C, Se, Si, S, Ge, Na, and Li), and the isolation species, (H and F), in GaN, as measured by Secondary Ion Mass Spectrometry (SIMS).(!') Samples containing implants of some of these species were annealed at devated temnperatures and the impurity profiles re-measured to establish the extent of any redistribution. Selected elements were also implanted into both AN and InN. 159
Mat. Res. Soc. Symp. Proc. Vol. 354 0 1995 Materials Research Society
EXPERIMENTAL
The samples were grown on semi-insulating, (100) GaAs substrates by Metal Organic Molecular Beam Epitaxy.(1 ) The GaN was grown at 600 'C using triethylgallium and atomic nitrogen from an Electron Cyclotron Resonance plasma source, (2.45 GHz, 200 W forward power). AN layers were grown with trimethylamine alane and nitrogen at 625 'C, while the InN was deposited at 500 'C using trimethylindium and nitrogen. The layers are found to be defective single crystal, with a high density of stacking faults and microtwins due to the lattice mismatch wit
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