Pulsed characterization of vertical gallium arsenide (GaAs) optically activated switches

Abstract

This paper presents the results of pulsed characterization experiments conducted on vertical GaAs optically activated switches. The voltage hold-off characteristics, optically activated switching properties and lifetime performance of the switches have been examined. An all solid state system has been used to assess the characteristics of epilayered and switches fabricated from liquid encapsulated Czochralski (LEC) and vertical gradient freeze (VGF) GaAs. Non-epilayered devices have also been fabricated from the former material. A range of voltages have been applied to the different switches, up to a maximum of 6.5 kV for the reverse biased VGF devices. The longest lifetime recorded was shots for a LEC device, in which case no damage was visible to the switch. Lifetimes of shots were also observed for the forward-biased devices. A simple model of the voltage dropped across the switch during closure has been developed which assisted in the reduction of the switch `on' resistance. Lifetime and post mortem studies suggest that, in these experiments, the switch closure was due to a single filament. It is concluded that operating a switch with more than one filament, or ensuring that a single filament does not occur in the same position twice, is an effective method for increasing device lifetime.