Effects of Field-Dependent Trapping and Detrapping on the Responses of Compensated GaAs Photoconductive Switches

• Published in: IEEE transactions on plasma science 2007-02, Vol.35 (1), p.93-99
• Main Authors: Kelkar, K., Islam, N.E., Kirawanich, P., Fessler, C.M., Nunnally, W.C., Kemp, W.T., Sharma, A.K.
• Format: Article
• Language: English
• Subjects: Analytical models; Conducting materials; Conductivity; Current carriers; Devices; Electric discharges; Electricity generation; Electronic switching systems; Exact sciences and technology; Gallium arsenide; Laser mode locking; lock-on; Microwave generation; Microwaves; nonlinear photoconductive switch; Optical pulses; Photoconductivity; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma devices; Plasma switches (e.g., spark gaps); Pocket; Reservoirs; semi-insulating; Switches; Trapped charge; Trapping
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2006.889292

In this paper, the response of a semi-insulating gallium arsenide photoconductive switch used in high-power microwave generation has been analyzed through experiment and simulation. The switch characteristics as a result of trapping and detrapping phenomena during a transient are studied. Analysis show that field-enhanced capture at high field locations during the onstate creates a temporary reservoir of trapped charge at different pockets in the device. Release of trapped charge and the subsequent injection of carriers from the contacts to maintain charge neutrality helps maintain conduction, which persists even after the laser pulse until all charges are transferred across the device. A model has been presented which can explain such phenomena as lock-on effect, persistent conductivity, and low-power requirement during transients. This phenomenon is unique to semi-insulating gallium arsenide and is primarily due to field-enhanced trapping and could be applicable to other materials that have similar characteristics