title: Johnson's figure of merit
text: # Johnson's figure of merit
  
  Johnson's figure of merit is a measure of suitability of a semiconductor material for high frequency power transistor applications and requirements. More specifically, it is the product of the charge carrier saturation velocity in the material and the electric breakdown field under same conditions, first proposed by Edward O. Johnson of RCA in 1965.
  
  Note that this figure of merit (FoM) is applicable to both field-effect transistors (FETs), and with proper interpretation of the parameters, also to bipolar junction transistors (BJTs).
  
  ## Example materials
  
  | Material | Saturation velocity $x10^5$ m/s | $V_{Breakdown}$ MV/cm | JFM Si=1.0 |
  | - | - | - | - |
  | Silicon | 1.0 | 0.3 | 1.0 |
  | GaAs | 1.5 | 0.4 | 2.7 |
  | SiC | 2.0 | 3.5 | 20 |
  | InP | 0.67 | 0.5 | 0.33 |
  | GaN | 2.5 | 3.3 | 27.5 |
  
  JFM figures vary wildly between sources - see external links and talk page.
  
  