Simulation studies of persistent photoconductivity and filamentary conduction in opposed contact semi-insulating GaAs high power switches

Abstract

A self-consistent, two-dimensional, time-dependent, drift-diffusion model is developed to simulate the response of high power photoconductive switches. Effects of spatial inhomogeneities associated with the contact barrier potential are incorporated and shown to foster filamentation. Results of the dark current match the available experiment data. Persistent photoconductivity is shown to arise at a high bias even under the conditions of spatial uniformity. Filamentary currents require an inherent spatial inhomogeneity, and are more likely to occur for low optical excitation. Under strong uniform illumination, the spatial nonuniformities were quenched as a result of a polarization-induced collapse in the internal fields. However, strong electric fields resulting at the contacts create a bipolar plasma, and hence, a virtual “double injection.”

Photopolarization Effect and Photoelectric Phenomena in Layered GaAs Semiconductors

“…For example, semiconductors with persistent photoconductivity can be used as many important applications. However the locking time of the dark current (i.e., an unstable dynamical state) is fundamentally related with material preparation (Joshi et al, 1999). According to the NDD effect, the locking time can possibly be prolonged and controlled.…”

Observation of abrupt first-order metal–insulator transition in Be-doped GaAs

“…2(b) semiconductor with an exponential current characteristic in the I2V curve, the magnitude of current measured in the relatively smaller region A (semiconductor) is much smaller than that in the larger region B (metal) above the MITÀV DS ; a measured conductivity s measured ¼ s semiconductor þ s metal % s metal because s semiconductor 5s metal after the MIT occurs. The abrupt MIT may be closely related to the phenomenon, ''avalanche breakdown or dielectric breakdown'' with filamentary conduction, caused by a high electric field in a pn junction device [8,12]. The breakdown has long remained unsolved in semiconductor physics; namely the identity of the breakdown and why the breakdown happens to be a high current jump even though an avalanche phenomenon is continuous and the filament is slender [8,19,20].…”

“…The abrupt MIT may be closely related to the phenomenon, ''avalanche breakdown or dielectric breakdown'' with filamentary conduction, caused by a high electric field in a pn junction device [8,12]. The breakdown has long remained unsolved in semiconductor physics; namely the identity of the breakdown and why the breakdown happens to be a high current jump even though an avalanche phenomenon is continuous and the filament is slender [8,19,20]. It has been understood that the current jump as breakdown was caused by a ''short-circuit'' with resistance zero owing to device breakdown.…”

“…For a representative application of the MIT, the current jump provides a nano-level heat source for melting of a material for development of the next generation non-volatile memory [4]. The jump has been actually observed in insulators, CeO 2 [4], CaCu 3 Ti 4 O 12 [5], yÀðBEDTÀTTFÞ 2 CsZnðSCNÞ 4 [6], GaAs [7][8][9][10][11][12]. Besides these, many materials showed the current jump.…”

A search for defect configurational changes in the post‐breakdown metastability of semi‐insulating GaAs

“…A number of possible mechanisms for the PCSS effect have been suggested [4][5][6] that do not involve any movement of atomic positions such as are found, for example in the EL2 → EL2* metastable transition [7]. On the other hand high energy electron states occurring as a result of the avalanche could, in principle, bring about a configurational change in one of the GaAs native defects with the resulting observed hysteresis effect.…”