The Figure of Merit of a Semiconductor Power Electronics Switch

The figure of merit (FOM) of a semiconductor device represents an important quality as it pertains to its performance limits and is often used to drive the technology development in a specific direction. Comparing the performances of switching power MOSFETs using their FOMs has become ubiquitous practice in power semiconductor and power electronics industries. In this paper, a critical review of the proposed power MOSFET FOMs is presented, and key limitations are discussed. It is shown that the quality factor ${Q}_{F2}={(}{\lambda {E}_{c}}/{R_{ \mathrm{\scriptscriptstyle ON},\textsf {sp}}}{)}$ along with ${Q}_{G}$ and ${T}_{j\textsf {max}}$ may be used to guide the development of future generations of power semiconductor device technologies for power electronics switching applications, where $\lambda $ and ${E}_{c}$ are the thermal conductivity and critical electric field strength for the avalanche breakdown of the semiconductor material, respectively, ${R}_{ \mathrm{\scriptscriptstyle ON},\textsf {sp}}$ is the specific on-state electrical resistance, ${Q}_{G}$ is the gate charge, and ${T}_{j\textsf {max}}$ is the maximum junction temperature of the semiconductor power device, respectively.