J.H. Hur

GaAs-based opto-thyristor for pulsed power applications

An optically gated, GaAs bipolar junction thyristor with a semi-insulating base layer, specifically developed for pulsed power applications, is reported, and initial device performance characteristics as a pulsed power switch are presented. The measured DC blocking voltage of the device was >600 V, peak pulsed current was >or=70 A, and the current rise rate was >1.4*10/sup 9/ A/s. These results demonstrate that GaAs based junction devices have significant potential as switching elements for pulsed power systems requiring very fast closing times. >

Lock‐on effect in pulsed‐power semiconductor switches

Certain high‐voltage pulsed‐power switches based on semi‐insulating GaAs or InP exhibit a ‘‘lock‐on’’ effect. In this paper, this effect is argued to be fundamentally a transferred‐electron effect, and its experimentally observed characteristics are explained. The lock‐on effect causes high forward drop and high power dissipation for certain pulsed‐power switches based on GaAs and various other direct‐gap materials.

Avalanche breakdown in p‐n AlGaAs/GaAs heterojunctions

Avalanche breakdown in abrupt p‐n AlGaAs/GaAs heterojunctions is invesigated, and the breakdown voltage, the maximum electric field, and the depletion layer width are calculated as functions of the doping densities, the temperature, and the AlAs mole fraction in AlGaAs. The model employed is an extension of Hauser’s model of homojunction breakdown [Appl. Phys. Lett. 33, 351 (1978)], and it includes the effects of the band offsets at the interface.

A high-voltage optoelectronic GaAs static induction transistor

Experimental realization of an optically activated, high-voltage GaAs static induction transistor (SIT) is reported. In the forward blocking state, the breakdown voltage of the device was approximately 200 V, while in the conduction state, on-state current densities exceeding 150 A/cm/sup 2/ were obtained. In the floating-gate configurations (gate open), the specific on-resistance of the device was approximately 50 m Omega -cm/sup 2/. Optical modulation of the device was achieved using a compact semiconductor laser array as the triggering source. In this mode, a gate-coupled RC network was implemented, resulting in an average switching energy gain (load energy/optical energy) of approximately 30. This mode of operation is applicable to series-coupled devices for pulsed switching at higher power levels.<<ETX>>

GaAs opto-thyristor for pulsed power applications

Results of an investigation of GaAs-based opto-thyristors for pulsed power applications are presented. In this study, semi-insulating GaAs was used for the base layer of the opto-thyristor, and the device was optically triggered with an AlGaAs laser diode. The blocking voltage of the opto-thyristor was >or=800 V, the peak pulsed current was approximately 300 A, and di/dt was >or=1.5*10/sup 10/ A/s. These results demonstrate that III-V based junction devices have significant potential for pulsed power switching applications.<<ETX>>

A comparative study of Si‐ and GaAs‐based devices for repetitive, high‐energy, pulsed switching applications

A study is performed to assess Si and GaAs as materials for realization of repetitive, high‐energy, pulsed switches in applications where the switching parameters are blocking voltages (VB) exceeding 1 kV in the off state and conduction currents (IF) in excess of 500 A in the on state, the current risetime being less than 1 μs and the pulse length being longer than 50 ns. Theoretical and technological limitations associated with the switching characteristics of Si‐ and GaAs‐based majority carrier (unipolar) and minority carrier (bipolar) devices in the low‐field, high‐mobility, and high‐field velocity saturation regimes are analyzed and discussed. It is concluded that for medium power applications (VBIF<300 kW,VB≳1 kV), majority carrier devices are best suited for fast switching processes in the low‐field, low current density (J<100 A/cm2) regime. Under such conditions, the high drift mobility of GaAs allows for realization of field‐effect devices exhibiting fast switching speeds and low on‐state conducti...

Lock-on effect in GaAs photoconductive switches

The lock-on effect observed in high power, light-activated GaAs bulk switches is very important in determining the GaAs power device performance. An analytical model to explain the physical origin of this effect is presented. In this model, negative resistance associated with transferred-electron effect creates high-field-induced avalanche injection at the anode contact. A regional approximation is used to calculate the field distribution in the device and to derive the device f-V characteristics. Reported experimental results are in good agreement with the model over a wide range of device parameters.

Optoelectronic bistability in gallium phosphide

An optoelectronic bistability in GaP is reported. The bistable mechanism which is based on trap filling is discussed, and possible applications are described. This simple bistable device can be realized using a commercial light‐emitting diode.

A HIGH VOLTAGE GaAs STATIC INDUCTION TRANSISTOR

Design, fabrication and pulsed switching characteristics of a high voltage GaAs static induction transistor (SIT) are reported. The SIT is a vertical channel field-effect transistor which exhibits intrinsic turn-on and turn-off capability. In the GaAs SIT, optoelectronic modulation allows for isolation of the signal source and the high side switch, which in turn results in improved reliability in high voltage, floating potential systems. DC characterization of the device was performed at room temperature and higher operating temperatures (2.5 C<T<2.50 C). In the forward blocking state, avalanche breakdown of the gate junction occurred at -200 V, while in the conduction state, current densities exceeding 150 A/cm2 were observed. In the floating gate configuration, the on-resistance of the device was -50 mQ.cm2, which is considerably lower than Si MOSFETs designed for equal values of ideal breakdown voltage. Pulsed switching tests were performed using electronic and optical triggering sources. Electrical triggering resulted in power gains as high as 80. Optical triggering was achieved using a GaAs-based laser diode array as the source. In this case, an energy gain (load energy/optical energy) of -30 was obtained. Issues pertaining to optimization and scaling of the device geometry for operation at higher power levels are discussed.

High speed static induction transistor for pulsed power applications

The proposed design and fabrication of a recessed-gate GaAs static induction transistor (SIT) are reported. The SIT is a vertical channel, field-effect switching device which exhibits gate-induced turn-on and turn-off and is well-suited for pulsed power applications. Modeling of the device has been performed to correlate the experimentally observed characteristics with calculated values upon fabrication. The base (channel) layer is grown by vapor phase epitaxy, and the dopant concentration and thickness of this layer are designed to achieve optimum device characteristics. The current risetime in the SIT is limited by the rate of decrease of the potential barrier in the channel as well as the transit time of carriers from the source to the drain region of the device. In this case, assuming that electrons travel across the drift region at saturation velocity, the transit time is calculated to be <500 ps.<<ETX>>