On the physics and modeling of small semiconductor devices-III. Transient response in the finite collision-duration regime

The role of the finite, non-zero collision duration in high electric fields is examined for its effect on transient and over-shoot response of the carrier velocity and energy. The finite collision duration introduces a temporal retardation effect on the collisional relaxation mechanisms for energy and momentum. As a consequence, the effective temperature also undergoes an overshoot behavior, which leads to a general quickening of the total transient response. Calculations were performed for steady, homogeneous fields utilizing a displaced Maxwellian approach. These calculations were performed for GaAs and Si and have significance for sub-micron devices in these materials. The generally faster response leads to the prospect of improved high frequency properties over what is normally expected.