Terence Burke

Sensitive optical gating of reverse-biased AlGaAs/GaAs optothyristors for pulsed power switching applications

A heterojunction-based optothyristor has been fabricated and tested with biasing field intensity up to 34 kV/cm for pulsed power applications. The reverse-biased optothyristor can even be triggered by a light-emitting diode (LED) of a few microwatts power, and more than 500 times reduction in the required LED power for triggering has been observed when compared to bulk photoconductive switches. The optothyristor, however, does not turn on under similar triggering conditions if bias polarity is changed. The sensitive optical gating of the reverse-biased optothyristor is explained. The turn-on delay time under reverse bias has been found to be inversely proportional to the square root of the LED power. The possibility of improving the switching efficiency by superimposing the laser pulse on a constant lower level background illumination has been demonstrated. >

An LPE grown InP based optothyristor for power switching applications

This paper presents the results of a new InP based optothyristor for pulsed high power switching applications and compares them with a traditional InP photoconductive switch operating under similar conditions. The optothyristor utilized a semi-insulating InP wafer inserted between the two PN junctions in a conventional thyristor structure. We also determined the dynamic I-V characteristics and the di/dt turn-on parameter for this novel optothyristor. Using a 1.06 /spl mu/m YAG laser to trigger the optothyristor, we have achieved a 1200 V (4.8/spl times/10/sup 4/ V/cm) hold-off voltage with a maximum current of 61 A. The current rise time for device turn-on was measured to be consistently under 12 ns, and a maximum di/dt of 1.4/spl times/10/sup 10/ A/s was obtained. >

A High Performance Optically Gated Heterostructure Thyristor Passivated with LT-GaAs

A high performance, Al 0.3 Ga 0.7 As/GaAs based, optically gated thyristor with a bulk semi-insulating(SI) GaAs 650 μm in thickness as the voltage blocking layer has been fabricated and characterized for high power pulsed switching applications. Low temperature(LT) GaAs was used to passivate the device surface and was found to greatly improve the switch hold-off voltage. The switched current as a function of bias up to 2,200 V (34 kV/cm) has been tested and the maximum switched current was 240 A with a di/dt equal to 2.02×10 10 A/s. The forward dynamic current-voltage characteristics have been measured and the dissipated energy per switching determined. It was found that very sensitive triggering of the switch is possible, even with a light emitting diode operating in the sub-mW range, when the thyristor is reverse biased. The sensitive triggering is a result of the carrier tunneling through the reverse biased pn junctions.

Field-And Time-Dependent Photo And Dark Current Studies Of Semi-Insulating Gaas

Photocurrent and dark current precise time-dependent measurements have been conducted on semi-insulating GaAs as functions of pulsed voltage at room and low temperature, employing pulsed and continuous illumination. These experiments have been performed also as functions of fast voltage interruptions and slow voltage interruptions and slow voltage relaxations, and their respective position in time (epoch) as well as the time of imposition of a field pulse. Further work was conducted on the response of photocurrent to follow rapidly oscillating cw voltage superimposed onto a field pulse. The objective of these studies is to assist in characterizing trapping levels in semi-insulating GaAs, including EL2, and to determine time-constants for current decay. From these experiments we deduced a trap saturation time of 300 ns and a trap liberation time of 8.5 - 10.0 ns.