Generation of coherent current pulses and delayed switching in relaxation GaAs p+-iν-n diodes

Abstract

In GaAs p+-ν-n diodes prepared from high-resistivity Cr-doped GaAs, generation of coherent current pulses (CCP) has been observed in the forward bias region Vth?V<Vsw and delayed switching in the region V≳Vsw, where Vth is a threshold voltage for the CCP and Vsw is a threshold voltage for the switching. Coexistence of multiple components of the CCP with different interpulse times and pulse heights has been observed, which indicates that the CCP is caused by the periodic formation and annihilation of the filamentary current path. A double-pulse experiment of the delayed switching has been performed using first and second identical pulses with varying pulse-separation time. For pulse heights slightly larger than Vsw, the delay time of the second pulse (td2) is larger than that of the first pulse (td1). Experimental results show that this peculiar relation td2≳td1 is due to an electronic process. These new nonlinear transport phenomena are closely related to each other. A model based on the concept of the relaxation semiconductor is proposed, taking into account the relationship between the dielectric relaxation time and the diffusion length lifetime in a transient state of the system involving two types of defect centers. Numerical estimations based on the model agree with the experimental values.