Hot-phonon temperature and lifetime in biased 4H-SiC

Experimental results on electron transport and microwave noise are used to investigate, in the electron temperature approximation, dissipation of hot-electron energy in a biased donor-doped 4H-SiC channel (n=2∙1017cm−3). The electron energy relaxation time is estimated to be 2.8±1ps in the electric-field range below 25kV∕cm at room temperature. Longitudinal-optical phonons are found responsible for electron energy dissipation when the supplied power ranges from 0.5to25nW per electron. In this range, accumulation of nonequilibrium (hot) longitudinal-optical phonons takes place. Equivalent hot-phonon temperature reaches 3000K near 30kV∕cm, hot-phonon lifetime is comparable to the electron energy relaxation time. Dependence of the lifetime on electric field is weak in the investigated range of electric fields below 50kV∕cm.