Residual sulphur and silicon doping in InP and GaInAs

Abstract

The samples studied here are either InP single crystals grown by the liquid encapsulation Czochralski technique or GaInAs epilayers grown on InP by molecular beam epitaxy or liquid phase epitaxy. They were characterized by secondary ion mass spectrometry (SIMS), Hall effect measurements, spark source mass spectrography (SSMS), and scanning electron microscopy (SEM). Quantitative high resolution SIMS analyses identify sulphur and silicon as background residual donors in these materials, but, it is found that the concentration of sulphur ranging from 4 × 10 15 to 8 × 10 16 cm −3 is about one order of magnitude higher than that of silicon. The donor concentrations determined either from electrical measurements or from SIMS analyses agree to within a factor of two over almost two orders of magnitude. Nevertheless, the behaviour of silicon in InP is still unclear. In homogeneous regions of the crystals, silicon is found by SIMS, at a low concentration, in the 3 × 10 14 –6 × 10 15 cm −3 range. But, sometimes, in regions where microtopographies are visible, perhaps precipitates or inclusions, the silicon concentration grows up to anomalously high levels. This fact is confirmed by bulk SSMS analyses.