Drift velocity saturation and large current density in an intrinsic three-dimensional Dirac semimetal cadmium arsenide

Transport of electrons at high electric fields is investigated in an intrinsic three-dimensional Dirac semimetal cadmium arsenide, considering the scattering of electrons from acoustic and optical phonons. Screening and hot phonon effect are taken in to account. Expressions for the hot electron mobility $\mu$ and power loss $P$ are obtained as a function of electron temperature $T_e$. The dependence of drift velocity $v_d$ on electric field $E$ and electron density $n_e$ has been studied. Hot phonon effect is found to set in the saturation of $v_d$ at relatively low $E$ and significantly degrades its magnitude. The drift velocity is found to saturate at a value $v_{ds} \sim 10^7$ cm/s and it is weakly dependent on $n_e$. A large saturation current density $\sim 10^6$ A/cm$^2$ is predicted.