TIN-DOPING OF N+ INP OMVPE LAYERS

Tin as a donor dopant in OMVPE epilayers of InP has been studied for its dependence on growth parameters to assess the nature of the dopant incorporation from a tetraethyltin (TESn) source and to establish reproducible conditions for tailoring carrier concentrations. Free carrier concentrations depend linearly on Sn/In ratio and are independent of PH3 concentration consistent with the impurity incorporation on In-lattice sites. The carrier concentration saturates at 3 x 10(19) cm-3 and is accompanied by excess Sn accumulation on the layer surface. X-ray diffraction shows an expansion of the lattice proportional both to the measured free carrier concentration and to the TESn gas concentration up to solid saturation. The lattice expansion is larger than expected from Sn for In radius substitution. SIMS profiles for abrupt turn-on and turn-off of the dopant source show transient changes of Sn concentration consistent with a Sn surface layer buildup.