There are continuing rapid developments in vertical geometry Ga2O3 for high voltage switching applications. Ga2O3 is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping and the availability of large diameter, relatively inexpensive substrates. These include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors and advanced power management and control electronics. There are already cases where the performance exceeds the theoretical values for SiC. Existing Si, SiC (vertical devices), and heteroepitaxial GaN (lateral devices) enjoy tremendous advantages in terms of process maturity, an advantage that is especially true for Si, where the ability to precisely process the material has resulted in devices such as super-junctions that surpass the unipolar “limit”. Continued development of low defect substrates, optimized epi growth and surface treatments and improved device design and processing methods for Ga2O3 are still required to push the experimental results closer to their theoretical values. Even 3 μm epi layers with doping concentration of 1016 cm-3 should have a theoretical breakdown voltage of ~1800V. The actual experimental value of VB is currently well below the theoretical predictions. Thermal management is a key issue in Ga2O3 power devices for practical high current devices and initial studies have appeared on both the experimental and theoretical fronts. We summarize progress in edge termination design, temperature measurement using thermoreflectance-based thermography to measure the thermal rise and decay of the active diodes, failure under forward bias and development of large current (up to 130A) arrays.
Reverse breakdown voltages larger than 1 kV have been reported for both unterminated Ga2O3 vertical rectifiers (1000- 1600 V) and field-plated Schottky diodes (1076-2300 V) with an epi thickness of 8-20 μm. If the doping is in the 1016 cm-3 range, the breakdown is usually in the 500-800V regime. Furthermore, the switching characteristics of discrete Ga2O3 vertical Schottky rectifiers exhibited reverse recovery times in the range of 20 to 30 ns. Large area (up to 0.2 cm2 ) Ga2O3 rectifiers were fabricated on a Si-doped n-Ga2O3 drift layer grown by halide vapor phase epitaxy on a Sn-doped n+ Ga2O3 (001) substrate. A forward current of 2.2 A was achieved in single-sweep voltage mode, a record for Ga2O3 rectifiers. The on-state resistance was 0.26 Ω·cm2 for these largest diodes, decreasing to 5.9 × 10-4 Ω·cm2 for 40x40 μm2 devices. We detail the design and fabrication of these devices. In addition, an inductive load test circuit was used to measure the switching performance of field-plated, edge-terminated Schottky rectifiers with a reverse breakdown voltage of 760 V (0.1 cm diameter, 7.85x10-3 cm2 area) and an absolute forward current of 1 A on 8 Μm thick epitaxial β-Ga2O3 drift layers. These devices were switched from 0.225 A to -700 V with trr of 82 ns, and from 1 A to -300 V with trr of 64 ns and no significant temperature dependence up to 125°C. There was no significant temperature dependence of trr up to 150°C.
Based on the measurement results of a 5 GHz CMOS radar microchip, it is shown that low power CMOS radar-on-chip
integration can have high detection sensitivity despite the large flicker noise and phase noise contributions around the
signal of interest. Key technologies to further increase the detection sensitivity will be discussed, including software
configured DC offset calibration, noise suppression using tunable baseband bandwidth limiter, and special receiver
architecture for flicker noise reduction. The applications of low-cost high-sensitivity on-chip radar will be focused on
surveillance and reconnaissance, sensing through-wall radar, ground penetration radar, border monitoring, and moving
Chemical sensors can be used to analyze a wide variety of environmental and biological gases and liquids and may
need to be able to selectively detect a target analyte. Different methods, including gas chromatography (GC),
chemiluminescence, selected ion flow tube (SIFT), and mass spectroscopy (MS) have been used to measure biomarkers.
These methods show variable results in terms of sensitivity for some applications and may not meet the requirements for
a handheld biosensor. A promising sensing technology utilizes AlGaN/GaN high electron mobility transistors (HEMTs).
HEMT structures have been developed for use in microwave power amplifiers due to their high two dimensional electron
gas (2DEG) mobility and saturation velocity. The conducting 2DEG channel of GaN/AlGaN HEMTs is very close to the
surface and extremely sensitive to adsorption of analytes. HEMT sensors can be used for detecting gases, ions, pH
values, proteins, and DNA. In this paper we review recent progress on functionalizing the surface of HEMTs for specific
detection of glucose, kidney marker injury molecules, prostate cancer and other common substances of interest in the
Wide bandgap semiconductor ZnO and GaN nanowires have shown the ability to detect many types of
gases, biological and chemical species of interest In this review we give some recent examples of using
these nanowires for pH sensing, glucose detection and hydrogen detection at ppm levels.
Getting to wounded soldiers on the battlefield is a precarious task, and medics have a very high casualty
rate. It is therefore a vital importance to prioritize which soldiers to attend to first. The first step is to detect
life signs - if a soldier is dead or alive, and prioritize recovery of live soldiers. The second step is to obtain
vital signs from live soldiers, and use this to prioritize which are in most urgent need of attention. Our
team at Kai Sensors, University of Hawaii and University of Florida is developing Doppler radar heart
sensing technology that provides the means to detect life signs, respiration and/or heart beat, at a distance,
even for subjects lying motionless, e.g., unconscious subjects, wearing body armor, and hidden from direct
view. Since this technology can deliver heart rate information with high accuracy, it may also enable the
assessment of a subject's physiological and psychological state based on heart rate variability (HRV)
analysis. Thus, the degree of a subject's injury may also be determined. The software and hardware
developments and challenges for life signs detection and monitoring for battlefield triage will be discussed,
including heart signal detection from all four sides of the human body, detection in the presence of body
armor, and the feasibility of HRV parameter extraction.
Wide bandgap semiconductor nanowires are attractive for a variety of sensing purposes because of their excellent
stability, large surface area, pizeo-electric nature and ability to be integrated with on-chip wireless communication
systems. In this brief review, we will discuss progress in these nanowires for gas sensing.
Technology for the detection of enemies from behind barriers and for securing of ports and perimeters with minimal
threat to warfighters is essential in modern threat scenarios. We are developing a network of small scattered Doppler
radar sensors which lie in wait and report on change or motion within a targeted perimeter. Most sensors are simple radar
receiver "nodes" capable of short range communications and long operation life with minimal power requirements,
while a few are more advanced radar transceiver "beacons" capable of active interrogation and long range
communications. Radar nodes and beacons could be scatter-deployed from a distance, creating a need for post-deployment
localization in order to provide useful reconnaissance. A beacon is designed to have absolute position
knowledge by strategic deployment of GPS, produces an interrogation signal, and analyzes locally received echoes for
signs of motion activity in the targeted area. Scattered nodes in the targeted vicinity form an ad-hoc network which also
receives and compares the beacon signal and its target echoes, and reports sensed activity to the beacon. This paper
introduces such a system and discusses radar node localization based on signal strength using kernel methods and
distributed learning algorithms which take energy constraints into account.
Technology that can be used to unobtrusively detect and monitor the presence of human subjects from a distance and
through barriers can be a powerful tool for meeting new security challenges, including asymmetric battlefield threats
abroad and defense infrastructure needs back home. Our team is developing mobile remote sensing technology for
battle-space awareness and warfighter protection, based on microwave and millimeter-wave Doppler radar motion
sensing devices that detect human presence. This technology will help overcome a shortfall of current see-through-thewall
(STTW) systems, which is, the poor detection of stationary personnel. By detecting the minute Doppler shifts
induced by a subject's cardiopulmonary related chest motion, the technology will allow users to detect personnel that are
completely stationary more effectively. This personnel detection technique can also have an extremely low probability of
intercept since the signals used can be those from everyday communications. The software and hardware developments
and challenges for personnel detection and count at a distance will be discussed, including a 2.4 GHz quadrature radar
single-chip silicon CMOS implementation, a low-power double side-band Ka-band transmission radar, and phase
demodulation and heart rate extraction algorithms. In addition, the application of MIMO techniques for determining the
number of subjects will be discussed.
Proc. SPIE. 4592, Device and Process Technologies for MEMS and Microelectronics II
KEYWORDS: Receivers, Signal to noise ratio, Silicon, Global system for mobile communications, Intermodulation, Signal detection, Interference (communication), Standards development, Switches, Transistors
Third generation (3G) cellular wireless systems are envisioned to offer low cost, high-capacity mobile communications with data rates of up to 2 Mbit/s, with global roaming and advanced data services. Besides adding mobility to the internet, 3G systems will provide location-based services, as well as personalized information and entertainment. Low cost, high dynamic-range radios, both for base stations (BS) and for mobile stations (MS) are required to enable worldwide deployment of such networks. A receiver's reference sensitivity, intermodulation characteristics, and blocking characteristics, set by a wireless standard, define performance requirements of individual components of a receiver front end. Since base station handles multiple signals from various distances simultaneously, its radio specifications are significantly more demanding than those for mobile devices. While high level of integration has already been achieved for second generation hand-sets using low-cost silicon technologies, the cost and size reduction of base stations still remains a challenge and necessity. While silicon RFIC technology is steadily improving, it is still difficult to achieve noise figure (NF), linearity, and phase noise requirements with presently available devices. This paper will discuss base station specification for 2G (GSM) and 3G (UMTS) systems, as well as the feasibility of implementing base station radios in low-cost silicon processes.