Incorporation of boron in SiGe(C) epitaxial layers grown by reduced pressure chemical vapor deposition

Abstract

In this paper the strain and electrical properties of epitaxial in situ B-doped (10 18–10 21 cm −3) SiGeC layers (23, 28% Ge and 0, 0.5% C) has been investigated. The growth rate was shown to have a significant increase at 3×10 −2 mTorr diborane partial pressure. This point coincides with an enhancement in boron incorporation, which was explained by the strain compensation effect of boron in the highly strained SiGeC layers. In these samples, the total Ge and C content was shown to remain constant with increasing diborane partial pressure. The substitutional/active dopant concentration in SiGe layers was obtained by high-resolution X-ray diffraction by measuring the strain compensation effect of boron. The interaction between C and B in SiGe matrix was also investigated. This was compared with the active dopant concentration obtained from Hall measurements in order to achieve a Hall scattering factor of 0.3–0.7 for dopant concentrations between 3×10 18 and 5×10 21 cm −3. The resistivity values of these layers were in the range 2×10 −2–4×10 −4 Ω cm. Finally, it was shown that boron atoms in SiGeC layers locate preferably at substitutional sites in contrary to carbon atoms at both substitutional and interstitial sites.