A Compact, Versatile Net Flux Radiometer for Ice Giant Probes

Advanced Microwave and Millimeter Wave Technologies Semiconductor Devices Circuits and Systems, 2010

Micro and Nano Letters, 2006

Rectification by a 50 A ˚ (5 nm) thick aluminium gallium nitride (AlGaN) polarisation barrier with maximum voltage swing of 27 V is demonstrated. In order to achieve a large voltage swing, the device is constructed with a 3000 A ˚ (300 nm) thick undoped gallium nitride (GaN) space charge layer adjacent to the barrier to enable a large voltage drop before the advent of impact ionisation breakdown. The spontaneous and piezoelectric polarisation discontinu-ities at the AlGaN/GaN interfaces determine the band profiles and the thermally assisted tunneling flux of electrons through the barrier. The 3.24 MV cm 21 electric field across the 50 A ˚ thick barrier at low bias enables efficient tunneling of electrons, despite the large effective electron mass of 0.19. The effective barrier seen by electrons changes from triangular to trapezoidal for one direction of bias and enhances the asymmetry effect. The demonstrated device characteristics show that wide band-gap polarisation barriers can potentially be used as the basic components of high-power microwave limiters.

IEEE Transactions on Electron Devices, 2020

In this article, we investigate defect nucleation leading to device degradation in β-Ga 2 O 3 Schottky barrier diodes by operating them inside a transmission electron microscope. Such in situ approach allows simultaneous visualization and quantitative device characterization, not possible with the current art of postmortem microscopy. High current density and associated mechanical and thermal fields are shown to induce different types of crystal defects, from vacancy cluster and stacking fault to microcrack generation prior to failure. These structural defects can act as traps for carrier and cause device failure at high biasing voltage. Fundamental insights on nucleation of these defects and their evolution are important from materials reliability and device design perspectives. Index Terms-β-Ga 2 O 3 , crystal defects, in situ transmission electron microscope (TEM), Schottky barrier diodes (SBDs). I. INTRODUCTION H IGH breakdown field of wide bandgap materials makes them well-suited to high power electronics applications [1]-[3]. Both GaN and SiC are commercialized for power switching and control systems, while materials with

Journal of Applied Physics, 2022

A top-illuminated deep-ultraviolet (DUV) Al0.6Ga0.4N p-in avalanche photodiode (APD) structure was designed, grown by metalorganic chemical vapor deposition on an AlN bulk substrate and on two different quality AlN/sapphire templates, and APDs were fabricated and tested. The APD devices with a circular diameter of 20 µm have demonstrated a distinctive reverse-bias breakdown behavior. The reverse breakdown voltage of the APDs is ~-140V, which corresponds to breakdown electric field of 6~6.2 MV/cm for the Al0.6Ga0.4N material as estimated by Silvaco TCAD simulation. The APDs grown on the AlN bulk substrate shows the lowest leakage current density of <1×10-8 A/cm 2 (at low reverse bias) compared to that of the devices grown on the AlN templates. From the photocurrent measurement, a maximum gain (current limited) of 1.2×10 4 is calculated. The average temperature coefficients of the breakdown voltage are negative for APD devices fabricated from both the AlN bulk substrate and the AlN templates, but these data show that the coefficient is the least negative for the APD devices grown on the lowdislocation-density AlN bulk substrate. Significance Statement We present new data on the properties of deep-UV AlxGa1-xN p-in avalanche photodiodes grown on bulk AlN substrates operating at ~250 nm. Few published reports currently exist for such devices and these previous reports lack a full description of the electrical properties. This paper describes the structure and growth of these devices compared with devices grown on sapphire

A novel lateral β-Ga2O3 schottky diode with high permittivity dielectric superjuction technique which circumvents the lack of p-type dopants in β-Ga2O3 for high voltage applications is demonstrated. The lateral drift region was depleted from the sides in reverse bias using dielectric polarization which helps support higher electric field in the drift layer compared to conventional schottky diode. The use of such a novel dielectric superjunction structure also allows to have higher doping in the drift layer without degrading the breakdown which results in low on resistance . A dielectric superjunction schottky barrier diode with a specific on resistance of 1.65 mΩ-cm2 and a breakdown voltage of 1487 V resulting in a power figure of merit of 1.35 GW/cm2 is demonstrated.

2000

Development of cryogenic readout circuits for Superconducting Tunneling Junction (STJ) direct detectors for submillimeter wave is presented. We chose a Capacitive Transimpedance Amplifier as a preamplifier design for the STJs because of relatively large impedance of the STJ. Using a SONY n-type GaAs Junction Field Effect Transistors (JFET), we measured electrical characteristics of the GaAs JFETs in the temperature range

IEEE Transactions on Electron Devices

The performance of ultra-wide band gap materials like-Ga2O3 is critically dependent on achieving high average electric fields within the active region of the device. In this report, we show that high-k gate dielectrics like BaTiO3 can provide an efficient field management strategy by improving the uniformity of electric field profile in the gate-drain region of lateral field effect transistors. Using this strategy, we were able to achieve high average breakdown fields of 1.5 MV/cm and 4 MV/cm at gate-drain spacing () of 6 m and 0.6 m respectively in-Ga2O3, at a high channel sheet charge density of 1.8 × 10 13 cm-2. The high sheet charge density together with high breakdown field enabled a record power figure of merit (2 /) of 376 MW/cm 2 at a gate-drain spacing of 3 m. Low loss power switching devices were mostly based on Si until the introduction of wide band gap semiconductors like SiC (3.2 eV, Fbr=2.5 MV/cm) and GaN (3.4 eV, Fbr=3 MV/cm). The much larger breakdown field strength in these semiconductors offered the possibility of shrinking the active drift region thickness for the same breakdown voltage resulting in much lower on resistance (). This improvement in the performance of power switching devices on breakdown field is well described by the power figure of merit 1 (BFOM-3), where , and represent dielectric permittivity, carrier mobility and breakdown field strength respectively. With a theoretical breakdown field strength (8 MV/cm) 2,3 much higher than GaN and SiC,-Ga2O3 offers a new material platform for improving the performance metrics of such devices. In addition to the large breakdown field strength, the availability of bulk substrates grown from melt 4-7 makes-Ga2O3 highly attractive since this

IEEE Transactions on Electron Devices, 2020

In this article, we investigate defect nucleation leading to device degradation in &lt;inline-formula&gt; &lt;tex-math notation=&quot;LaTeX&quot;&gt;$\beta $ &lt;/tex-math&gt;&lt;/inline-formula&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Schottky barrier diodes by operating them inside a transmission electron microscope. Such &lt;italic&gt;in situ&lt;/italic&gt; approach allows simultaneous visualization and quantitative device characterization, not possible with the current art of postmortem microscopy. High current density and associated mechanical and thermal fields are shown to induce different types of crystal defects, from vacancy cluster and stacking fault to microcrack generation prior to failure. These structural defects can act as traps for carrier and cause device failure at high biasing voltage. Fundamental insights on nucleation of these defects and their evolution are important from materials reliability and device design perspectives.

Materials Research Society Symposium Proceedings, 2008

In this work we focus on the fabrication of ohmic contacts and of Schottky barrier devices (SBD) on non-polar cubic GaN epilayers grown by molecular beam epitaxy (MBE). A Ti/Al/Ni/Au metallization was used for ohmic contacts and the contact resistance was measured by transmission line measurements (TLM). Ni, Pd, Ag and NiSi Schottky barrier devices 300 µm in diameter were fabricated by thermal evaporation using contact lithography on cubic GaN epilayers. The current-voltage (I-V) and the capacity-voltage (C-V) characteristics were studied at room temperature in detail. A clear rectifying behavior was measured in all SBDs. In the Ni and Ag SBDs an abnormal large leakage current under reverse bias was observed. Isochronal thermal annealing of these Ni and Ag based SBDs at 200°C in air improved the reverse characteristics by up to three orders of magnitude. This is in contrast to the Pd contacts, where the as grown contact showed already good performance and thermal annealing had nearly no influence on the I-V characteristics. For all SBDs the magnitude of the reverse current is generally larger than that expected due to thermionic emission and an exponential increase of the reverse current is observed with increasing reverse voltage. In-depth analysis of the I-V characteristic showed that a thin surface barrier is formed at the metal semiconductor interface and that crystal defects like dislocations may be the reasons for the discrepancy between experimental data and thermionic emission theory.

Semiconductor Science and Technology, 2011

Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 m cm 2 and a maximum breakdown voltage of 600 V, resulting in a figure-ofmerit of 275 MW cm −2 . An ultra-low reverse leakage current density of 3.7 × 10 −4 A cm −2 at reverse bias of 400 V was observed. Temperature-dependent I-V measurements were also carried out to study the forward and reverse transportation mechanisms.