The lock-on effect and collapsing bipolar Gunn domains in high-voltage GaAs avalanche p-n junction diode

TL;DR

This paper provides experimental and simulation evidence of the lock-on effect in high-voltage GaAs avalanche diodes, where the diode remains in a conducting state due to collapsing Gunn domains, defying typical recovery expectations.

Contribution

It introduces the first detailed analysis of the lock-on effect in GaAs avalanche diodes, highlighting the role of collapsing Gunn domains in sustaining conduction.

Findings

Diode remains conducting for dozens of nanoseconds after avalanche initiation.

Impact ionization occurs in collapsing Gunn domains and ionizing regions.

The lock-on effect is driven by negative differential mobility in GaAs.

Abstract

We present experimental evidence and physics-based simulations of the lock-on effect in high-voltage GaAs avalanche diodes. The avalanche triggering is initiated by steep voltage ramp applied to the diode and in-series 50 Ohm load. After subnanosecond avalanche switching the reversely biased GaAs diode remains in the conducting state for the whole duration of the applied pulse (dozens of nanoseconds). There is no indication of the p-n junction recovery that is commonly expected to develop on the nanosecond scale due to the drift extraction of non-equilibrium carriers. The diode voltage keeps a constant value of ~70 V much lower than the stationary breakdown voltage of 400 V. Numerical simulations reveal that the conducting state is supported by impact ionization in narrow high-field collapsing Gunn domains as well as in quasi-stationary cathode and anode ionizing domains. Collapsing Gunn domains spontaneously appear in the dense electron-hole plasma due to the negative differential mobility of electrons in GaAs. The effect resembles the lock-on effect of GaAs bulk photoconductive switches but is observed in reversely biased p-n junction diode switched by a non-optical method.