TEMPERATURE DEPENDENCE OF HOT ELECTRON DRIFT VELOCITY IN SILICON AT HIGH ELECTRIC FIELD

A time independent space-charge perturbation theory based on the avalanche multiplication process in a high field region is developed to correlate the measured space-charge resistance with the saturated hot electron drift velocity. The saturated hot electron drift velocity in Si observed at room temperature is 1.05 × 107 cm/sec to within 10 per cent in the field range 1.5 × 105 < E < 4 × 105 V/cm. The temperature variation of the hot electron drift velocity in Si is approximately 40 per cent between 77° and 490°K for electric fields higher than 2 × 105 V/cm. A phenomenological theory based on first principles and the electron-phonon interactions has also been derived to account for the temperature variation of the saturated hot electron drift velocity in Si. The physical consequence of the experimental result shows that the overall coupling between various branches of energetic phonons near the edge of the Brillouin zone and hot electrons should be stronger than that between long wavelength acoustic phonons and hot electrons. It also shows that the coupling between the combined LO and TO phonons near the edge of the Brillouin zone and hot electrons should be much stronger than that between the TA phonon near the edge of the Brillouin zone and hot electrons. From a practical standpoint, the result of this work suggests that if p-i-n diodes are used as photodetectors, one of the ultimate frequency responses of such a device is more essentially controlled by the width of the space-charge region in the device structure than by the effect of temperature variation. © 1968.