Query: Progress in gallium arsenide photoconductive switch research for high power applications

Candidate papers:

abstract: Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS) have been studied as an enabling technology for a variety of applications at both the Air Force Research Laboratory and Sandia National Laboratories. High gain PCSS can be triggered with small laser diodes or laser diode arrays. The requirements of these applications require the switching of high voltage in sub nanosecond time with low temporal jitter of the switches relative to the trigger laser. There have been several configurations and sizes of these switches studied by the Air Force Research Laboratory over the last several years. The most recent designs are with small structures where the electrical contacts are placed on opposite sides of the bulk material. This configuration allows for different electrical conditions on either side depending on the nature of the semiconductor structure; i.e. p i n or n i n. In addition to the type of structure used and geometry of the contacts, the performance of these switches (switch time, voltage, and jitter) is dependent on the thickness of the GaAs. Several thicknesses have been studied during the past year. This paper reports on the results of several studies to investigate the ultra fast switching properties of these structures.
author_names: Jonathan Gaudet

William D Prather

J W Burger

Michael C Skipper

Michael D Abdalla

Alan Mar

Martin W O'Malley

Fred J Zutavern

Guillermo M Loubriel
title: Progress in gallium arsenide photoconductive switch research for high power applications
venue: Conference Record of the Twenty Fifth International Power Modulator Symposium, 2002 and 2002 High Voltage Workshop.
year: 2002

abstract: An opposed contact photoconductive semiconductor switch, with a n+ region next to the cathode electrode has been simulated. Physical conditions during the pulse charging state, prior to high power switching, are analyzed in order to explain the increased hold off characteristic of such devices. Results show that the introduction of the n+ region near the cathode inhibits the flow of electrons at the n+/semi insulating interface until very high fields are reached. The formation of trap filled regions near the contacts and the resultant inhomogeneous device characteristics that lead to breakdown are thereby shifted to higher voltages. Thus, for switches with a n+ region next to the cathode, the breakdown voltage due to unstable filamentary conduction is also increased beyond those achieved previously, allowing for higher power operation.
author_names: Naz E Islam

Edl Schamiloglu

Charles B Fleddermann

Jon S H Schoenberg

Ravi P Joshi
title: Analysis of high voltage operation of gallium arsenide photoconductive switches used in high power applications
year: 1999

abstract: Electron injection and the subsequent formation of a trap filled region leads to premature device failure in an opposed contact, EL2/carbon compensated GaAs photoconductive switch, made through the liquid encapsulated Czochralski process. Due to the electrostatic properties associated with an n/sup /semi insulating junction, the introduction of an n/sup region next to the cathode suppresses electron injection until higher bias. The doping level, length, and the thickness of the high n/sup region are some of the parameters that affect hold off characteristics. Extending the length of the n/sup region well beyond the cathode does not increase the hold off voltage but confines current flow to a narrow strip, which may trigger local heating burnout. Suppression of the effects of the EL2 traps at the n/sup /SI interface also does not improve the hold off characteristics. Opposed contact switches, made from intrinsic GaAs have the characteristics of 'relaxation' semiconductors. The injection of minority carrier results in initial recombination and the formation of a large number of recombination regions may contribute to switching delays and jitters.
author_names: Naz E Islam

Edl Schamiloglu

Charles B Fleddermann

Jon S H Schoenberg

Ravi P Joshi
title: Improved hold off characteristics of gallium arsenide photoconductive switches used in high power applications
venue: Digest of Technical Papers. 12th IEEE International Pulsed Power Conference. (Cat. No.99CH36358)
year: 1999

abstract: There is considerable demand within the technical applications community for sources which produce high power transient radiation. Lateral geometry high power photoconductive semiconductor switches (PCSS) are being developed for use in phased array, ultra wideband sources. The present source configuration is a stacked Blumlein configuration commuted with a PCSS. A new liquid insulating media, HFE 7100, has been demonstrated to have an equivalent voltage hold off capability as sulphur hexafluoride, but with greater compatibility to gallium arsenide. Independent low jitter PCSS operation is demonstrated by coupling two independent Blumleins into a common load. Measurements of both the system jitter and the isolated jitter of the PCSS switch has been performed.
author_names: Jane M Lehr

Michael D Abdalla

Jon S H Schoenberg

Michael C Skipper

J Scott Tyo

J W Burger
title: Progress toward a compact, high power ultra wideband array using gallium arsenide photoconductive semiconductor switches
venue: Conference Record of the Twenty Third International Power Modulator Symposium (Cat. No. 98CH36133)
year: 1998

abstract: There is considerable demand within the technical applications community for sources which produce high power transient radiation. Currently, lateral geometry high power photoconductive semiconductor switches (PCSS) are being developed for use in phased may, ultra wideband sources. The present source configuration is a stacked blumlein configuration commuted with a PCSS. A new liquid insulating media, HFE 7100, has been demonstrated to have an equivalent voltage hold off capability as sulphur hexafloride, but with greater compatibility to gallium arsenide. Independent low jitter PCSS operation is demonstrated by coupling two independent blumleins into a common load. Measurements of both the system jitter and the isolated jitter of the PCSS switch has been performed.
author_names: Kirtland Afb
title: Progress Toward a Compact, High Power Ultra wideband Array using Gallium Arsenide Photoconductive Semiconductor Switches
year: 1998

abstract: Semi insulating gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS) have great potential for high voltage switching application, however, the utility is restricted by surface flashover which would result in breakdown. In this paper, a model of photo activated charge wave was proposed based on the theory of photo activated charge domain (PACD) in GaAs PCSS, and moderate suppression of PACD formation by loading the semiconductor surface with dielectric material was investigated theoretically and experimentally. Current as high as 3.7 kA was obtained at 28 kV, implying that this method can effectively inhibit the surface flashover and improve the service life of DC charged GaAs PCSS.
author_names: Ming Xu

Wei Shi

Zeng-gong Jiang

Shaoqiang Wang

Zhanglong Fu
title: Experimental Research on Inhibition of Surface Flashover Based on High Power Gallium Arsenide Photoconductive Switches Triggered by Laser
year: 2011

abstract: The electrical properties of semi insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle detectors and photoconductive semiconductor switches (PCSS) PCSS made from these materials operating in both the linear and non linear modes have applications such as firing sets, as drivers for lasers, and in high impedance, low current Q switches or Pockels cells. In the non linear mode, it has also been used in a system to generate Ultra Wideband (UWB) High Power Microwaves (HPM) The choice of GaAs over silicon offers the advantage that its material properties allow for fast, repetitive switching action. Furthermore photoconductive switches have advantages over conventional switches such as improved jitter, better impedance matching, compact size, and in some cases, lower laser energy requirement for switching action. The rise time of the PCSS is an important parameter that affects the maximum energy transferred to the load and it depends, in addition to other parameters, on the bias or the average fieldmore across the switch. High field operation has been an important goal in PCSS research. Due to surface flashover or premature material breakdown at higher voltages, most PCSS, especially those used in high power operation, need to operate well below the inherent breakdown voltage of the material. The lifetime or the total number of switching operations before breakdown, is another important switch parameter that needs to be considered for operation at high bias conditions. A lifetime of {approximately} 10{sup 4} shots has been reported for PCSS's used in UWB HPM generation [5] while it has exceeded 10{sup 8} shots for electro optic drivers. Much effort is currently being channeled in the study related to improvements of these two parameters high bias operation and lifetime improvement for switches used in pulsed power applications. The contact material and profiles are another important area of study. Although these problems are being pursued through the incorporation of different contact materials and introducing doping near contacts, it is important that the switch properties and the conduction mechanism in these switches be well understood such that the basic nature of the problems can be properly addressed. In this paper the authors report on these two basic issues related to the device operation, i.e. mechanisms for increasing the hold off characteristics through neutron irradiation, and the analysis of transport processes at varying field conditions in trap dominated SI GaAs in order to identify the breakdown mechanism during device operation. It is expected that this study would result in a better understanding of photoconductive switches, specifically those used in high power operation. less
author_names: Edl Schamiloglu

Alan Mar

Guillermo M Loubriel

Fred J Zutavern
title: Characteristics of trap filled gallium arsenide photoconductive switches used in high gain pulsed power applications
year: 2000

abstract: ABSTRACT Photoconductive semiconductor switches (PCSS) presently have the greatest potential fordramatic performance enhancements for high power pulsed applications. However, surface flashover severely limits the maximum stand off voltage in the open state. We report theuse of a novel technique to PCSS to overcome this limitation. The technique is anextension of the graded ring bushing idea from accelerator technology, but differs byreducing the thickness of the insulator (semiconductor) down to tens of micrometers. Recent results using this technique have yielded electric field values, before flashover, in the range of 70 kY/cm to 114 kVF/cm in silicon and 70 kY/cm to 84 kV/cm in gallium arsenide. 1. INTRODUCTION Photoconductive switch development is being pursued in several research programs.Results with GaAs switches capable of delivering 26 MW in 6Ons pulses, and current densities of up to 100 kA/cm2 have been obtained. Research done at Los Alamosdemonstrated a 200MW silicon switch operating at 150 kV and a peak current of 3 kA,
author_names: Juan M Elizondo

William M Moeny

Kevin Youngman
title: SILICON AND GALLIUM ARSENIDE VACUUM SURFACE FLASHOVER
venue: Ninth IEEE International Pulsed Power Conference
year: 1993

abstract: electronics circuits aiming to benefit from low turn on voltages and high speed. The fabrication of Schottky rather than pn diodes allows the turn on voltage to be reduced significantly below that suggested by the bandgap energy. This particularly impacts gallium nitride (GaN) devices, since the large ~3V turn on of pn diodes leads to large power losses in switching applications. However, Schottky diodes tend to have lower breakdown voltages and higher on resistance than pn devices. Improving breakdown with thicker drift layers tends to increase on resistance. High speed arises from the domination of current flow by majority carriers so that switching does not have to wait for the recombination of electron and holes. However, as frequencies increase to the terahertz and submillimeter wavelength level, fabrication becomes challenging due to the more restricted size of the device and high sensitivity to parasitic elements. Here we look at recent research progress for GaAs (gallium arsenide) and GaN Schottky barrier diodes.
author_names: M J Cooke
title: Boosting speed breakdown voltage performance of Schottky barrier diodes
year: 2017

abstract: Wide bandgap semiconductors have expanded the scope of device applications beyond those of silicon and gallium arsenide. Exploitation of wide bandgap semiconductors holds promise for revolutionary improvements in the cost, size, weight and performance of a broad range of military and commercial microelectronic and opto electronic systems. The inherent material properties of silicon carbide, gallium nitride and aluminum nitride make them ideal candidates for high power, high temperature electronics, power amplifiers, switches, and shortwavelength light sources. Gallium nitride based semiconductor technology has provided the fundamental basis for a new class of opto electronics. New electronic device structures based on silicon carbide and/or gallium nitride have demonstrated remarkable performance and are being considered for next generation military radar and commercial wireless applications. Additionally, silicon carbide devices have been demonstrated that exhibit superior high efficiency power switching capability, potentially leading to new capabilities in power distribution as well as electric vehicle technology. Critical to the realization of these enabling capabilities are the availability of high quality affordable substrate materials. The Department of Defense has invested heavily in bulk growth research and development of silicon carbide, gallium nitride and more recently aluminum nitride. A synopsis of current capabilities and future challenges for commercialization of these materials will be discussed. INTRODUCTION Semiconductor substrates provide the foundation for a multi $100B's electronics industry. Silicon is currently and will remain the material of choice for the foreseeable future due to the low cost, readily availability, and established device technology and infrastructure. If a device can be made with silicon it will. In spite of the phenomenal progress being made with silicon technology it does have its limitations with respect to temperature, frequency operation and voltage blocking capabilities. As gallium arsenide (GaAs) and indium phosphide (InP) technologies provided the basis for the phenomenal growth in the wireless and telecommunications industries during the late 1980s 1990s, a new class of semiconductors commonly referred to as "wide bandgap semiconductors" holds promise for continued revolutionary improvements in the size, cost, weight and performance of a broad range of military and commercial microelectronic and optoelectronic applications. Silicon carbide (SiC) gallium nitride (GaN) and more recently aluminum nitride (AlN) have emerged as candidate substrate materials that may overcome the performance limitations of silicon, GaAs and InP. SiC is clearly the most developed material of the three due to materials development efforts initiated in the mid 1980's, and the leadership of one company, Cree, Inc. in the maturation of the materials technology.
author_names: J D Blevins
title: Wide Bandgap Semiconductor Substrates Current Status and Future Trends
year: 2004