2.2.1 High Temperature Device Operation

The wide bandgap energy and low intrinsic carrier concentration of SiC allow SiC to maintain semiconductor behavior at much higher temperatures than silicon, which in turn permits SiC semiconductor device functionality at much higher temperatures than silicon. As discussed in basic semiconductor physics textbooks [37], semiconductor electronic devices function in the temperature range where intrinsic carriers are negligible so that conductivity is controlled by intentionally introduced dopant impurities. Furthermore, the intrinsic carrier concentration n$_{i}$ given by

$$n_{i} = \sqrt{N_\mathrm{c}\cdot N_\mathrm{v}}\cdot \exp \left( -\displaystyle\frac{E_{\mathrm{g}}}{2\cdot{\mathrm{k_B}}\cdot T_\mathrm{L}}\right)$$ (2.1)

is a fundamental prefactor to well-known equations governing undesired junction reverse-bias leakage currents [40]

$$\frac{J_\mathrm{leakage}}{{\mathrm{q}}} = n_{i}\cdot\displaystyle... ...m{A}} + \displaystyle\frac{D_\mathrm{p}}{L\mathrm{p}\cdot N_\mathrm{D}}\right).$$ (2.2)

With increasing temperature, the concentration of intrinsic carriers increases exponentially so that undesired leakage currents grow unacceptably large, and eventually at still higher temperatures, the semiconductor device operation is overcome by uncontrolled conductivity as intrinsic carriers exceed intentional device dopings. Depending upon specific device design, the intrinsic carrier concentration of silicon generally confines silicon device operation to junction temperatures less than 300$~^{\circ}$C. SiC's much smaller intrinsic carrier concentration theoretically permits device operation at junction temperatures exceeding 800$~^{\circ}$C, and 600$~^{\circ}$C device operation has been experimentally demonstrated on a variety of SiC devices [41,42]. T. Ayalew: SiC Semiconductor Devices Technology, Modeling, and Simulation