Interdiffusion in GaAs bipolar structures

Abstract

Emitter, base, and collector layers of GaAs with a nominal thickness of 0.5 /spl mu/m each were grown by organometallic vapor phase epitaxy (OMVPE). Each layer contained concentration spikes of the interdiffusion marker, indium. Annealing was performed in an open tube system for 1 h at T=900/spl deg/C using a controlled arsenic pressure. The dopants used, tellurium and carbon, reside on the group V sublattice and they are not expected to induce the so-called kick-out diffusion mechanism. The measured interdiffusion results are consistent with native defect concentrations' which approach their equilibrium values during the annealing process. A small emitter push effect can be measured for npn structures. We find that a Ga vacancy, with a charge of -1, provides a consistent explanation for interdiffusion in both n-type and p-type GaAs over the range of carrier density n=1/spl times/10/sup 19/ cm/sup -3/ to p=1/spl times/10/sup 19/ cm/sup -3/.