Defects and carrier compensation in semi-insulating4H−SiCsubstrates

Abstract

Electron paramagnetic resonance (EPR) studies revealed that vacancies (${V}_{\mathrm{C}}$ and ${V}_{\mathrm{Si}}$), carbon vacancy-antisite pairs $({V}_{\mathrm{C}}{C}_{\mathrm{Si}})$ and the divacancy $({V}_{\mathrm{C}}{V}_{\mathrm{Si}})$ are common defects in high-purity semi-insulating (HPSI) $4H\text{\ensuremath{-}}\mathrm{Si}\mathrm{C}$ substrates. Their concentrations and some of their deep acceptor levels were estimated by EPR and photoexcitation EPR. The commonly observed thermal activation energies, ${E}_{a}\ensuremath{\sim}0.8--0.9\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, $\ensuremath{\sim}1.1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, $\ensuremath{\sim}1.25--1.3$, and $\ensuremath{\sim}1.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, as determined from the temperature dependence of the resistivity, in different types of HPSI substrates were associated to different deep acceptor levels of ${V}_{\mathrm{Si}}$, ${V}_{\mathrm{C}}$, ${V}_{\mathrm{C}}{C}_{\mathrm{Si}}$, and ${V}_{\mathrm{C}}{V}_{\mathrm{Si}}$. The annealing behavior of these vacancy-related defects and their interaction at high temperatures (up to $1600\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ in HPSI materials were studied. Carrier compensation processes were proposed to explain the observed change of the thermal activation energy due to high temperature annealing. ${V}_{\mathrm{C}}$ and ${V}_{\mathrm{C}}{V}_{\mathrm{Si}}$ were suggested to be suitable defects for controlling the SI properties whereas the incorporation of ${V}_{\mathrm{Si}}$ and ${V}_{\mathrm{C}}{C}_{\mathrm{Si}}$ during the crystal growth or processing should be avoided for achieving stable HPSI materials.