<title>Characterization of vertical GaAs optically activated switches</title>

Abstract

In this paper we report on the experimentation conducted on vertical optically activated switches fabricated from GaAs grown by Liquid Encapsulated Czochralski (LEC) and Vertical Gradient Freeze (VGF) techniques. Heavily doped contact regions have been grown on the bulk GaAs to form n-SI GaAs-n and p-S1 GaAs-n structures. Dark dc I-V characterisation has been used to assess the voltage withstand characteristics of the devices demonstrating 3.5kV hold-off for reverse biased LEC and VGF p-SI GaAs-n devices. Optical activation has achieved a ins switch closure time with VGF p+-SI GaAs-n devices reverse biased at 7kV and 2ns switch closure times for VGF n-SI GaAs-n devices biased at 4.5kV. The voltage drop across the optically activated switches was characterised in terms of two components; a constant and a resistive voltage drop.

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

“…In contrast the forward-biased p + -i-n + and epilayered n +i-n + devices all have similar breakdown fields of about 40 kV cm −1 which is consistent with ohmic behaviour of the devices. The dark DC I -V characteristics reported previously for the epilayered switches [12] support these conclusions.…”

“…Dark DC experiments previously conducted on the VGF n +i-n + switches [12] revealed characteristics that were not expected for this type of device. It is thought that the unexpected performance of these switches may have been due to difficulties encountered in processing both sides of the GaAs which may have caused a parasitic p-type layer to form on one of the n + epilayers.…”

“…Current conduction ceased after the field across the switch fell below 6 kV cm −1 . This is the field required to support the nonlinear conduction mechanism in the device and is widely known as the lock-on field [12].…”