Johnson's figure of merit is a measure of suitability of a

semiconductor A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...

material for high frequency power transistor applications and requirements. More specifically, it is the product of the

charge carrier In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes. The term is used ...

saturation velocity Saturation velocity is the maximum velocity a charge carrier in a semiconductor, generally an electron, attains in the presence of very high electric fields. When this happens, the semiconductor is said to be in a state of velocity saturation. Ch ...

in the material and the

electric breakdown Electrical breakdown or dielectric breakdown is a process that occurs when an electrical insulating material, subjected to a high enough voltage, suddenly becomes an electrical conductor and electric current flows through it. All insulating mat ...

field under same conditions, first proposed by Edward O. Johnson of

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

in 1965."Physical limitations on frequency and power parameters of transistors," RCA Review, vol. 26, pp. 163-177, June 1965. Note that this

figure of merit A figure of merit is a quantity used to characterize the performance of a device, system or method, relative to its alternatives. Examples *Clock rate of a CPU * Calories per serving *Contrast ratio of an LCD *Frequency response of a speaker * ...

(FoM) is applicable to both

field-effect transistors The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contr ...

(

FET The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contr ...

s), and with proper interpretation of the parameters, also to

bipolar junction transistors A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...

(

BJT A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...

s).

Example materials

Gallium Nitride as an Electromechanical Material. R-Z. IEEE 2014
Table IV (p 5) JFM figures vary wildly between sources - see external links and talk page.

External links

Gallium Nitride as an Electromechanical Material. R-Z. IEEE 2014
Table IV (p 5) lists JFM (relative to Si) : Si=1, GaAs=2.7, SiC=20, InP=0.33, GaN=27.5, also shows V_sat and E_breakdown.

gives very different figures (but no refs) : Si GaAs GaN SiC diamond JFM 1 11 790 410 5800

References

Semiconductors {{materials-sci-stub