Optical and electronic properties of heavily boron-doped homo-epitaxial diamond

Abstract

At room temperature, the optical, transport and magnetotransport properties of homo-epitaxial MPCVD diamond layers with boron contents in the 2 × 10 20 to 2 x 10 21 cm -3 range are expected to be governed by the characteristics of the boron impurity band. A comparison of room temperature infrared transmittance, reflectance and visible ellipsometry spectra to temperature-dependent Hall effect and conductivity measurements allows a quantitative determination of optical constants and of transport parameters. The results are discussed in reference to the metallic-insulator transition in heavily doped semiconductors. This description enables us to discuss the Raman spectra of p + monocrystalline diamond, focussing on the polarization dependence of the low energy tail, of the unassigned broad peak observed around 500 cm -1 and of the optical phonon frequency range where the Fano interference occurs. On the basis of the observed scattering selection rules, we propose that these features result from electronic scattering in the impurity band and from the electron-phonon coupling on the boron center.