Photon counting detectors are used in many diverse applications and are well-suited to situations in which a weak signal is present in a relatively benign background. Examples of successful system applications of photon-counting detectors include ladar, bio-aerosol detection, communication, and low-light imaging. A variety of practical photon-counting detectors have been developed employing materials and technologies that cover the waveband from deep ultraviolet (UV) to the near-infrared. However, until recently, photoemissive detectors (photomultiplier tubes (PMTs) and their variants) were the only viable technology for photon-counting in the deep UV region of the spectrum. While PMTs exhibit extremely low dark count rates and large active area, they have other characteristics which make them unsuitable for certain applications. The characteristics and performance limitations of PMTs that prevent their use in some applications include bandwidth limitations, high bias voltages, sensitivity to magnetic fields, low quantum efficiency, large volume and high cost.Recently, DARPA has initiated a program called Deep UV Avalanche Photodiode (DUVAP) to develop semiconductor alternatives to PMTs for use in the deep UV. The higher quantum efficiency of Geiger-mode avalanche photodiode (GM-APD) detectors and the ability to fabricate arrays of individually-addressable detectors will open up new applications in the deep UV. In this paper, we discuss the system design trades that must be considered in order to successfully replace low-dark count, large-area PMTs with high-dark count, small-area GM-APD detectors. We also discuss applications that will be enabled by the successful development of deep UV GM-APD arrays, and we present preliminary performance data for recently fabricated silicon carbide GM-APD arrays.
The reverse voltage current characteristics and electroluminescence of small area 4H–SiC avalanche photodiodes were investigated and correlated with the presence of threading screw and edge dislocations. Localized electroluminescence was observed at threading dislocations at voltages close to breakdown whereas diodes without any extended defects exhibited uniform light emission in the active area. Diodes containing either edge or screw dislocations were found to have excess leakage currents and breakdown prematurely compared to diodes without dislocations.
Articles you may be interested inCarrier compensation near tail region in aluminum-or boron-implanted 4H-SiC (0001) J. Appl. Phys. 98, 043709 (2005); 10.1063/1.2030411Defect levels and types of point defects in high-purity and vanadium-doped semi-insulating 4H-SiC Electrical and microstructural properties of highly boron-implantation doped 6H-SiC A graphite mask was used to realize selective doping of aluminum/boron in 4H-SiC by thermal diffusion at a temperature range of 1800-2100°C. The doping profiles investigated by secondary ion mass spectrometry show that a high aluminum concentration of 5ϫ10 19 cm Ϫ3 near the surface and linearly graded boron profile up to several micrometers in depth can be obtained. Hall effect measurement was also employed to obtain the electrical characteristics of the diffused region, from which the carrier concentration ͑1ϫ10 19 cm Ϫ3 ͒ and hole mobility ͑7 cm 2 /V s͒ at room temperature were extracted. Room temperature photoluminescence indicates that the dominant luminescence is attributed to the donor acceptor pair recombination, in which boron D complex is the prevailing center rather than Al and boron shallow acceptors. Cathodoluminescence micrographs clearly illustrate a pattern with the locally diffused regions. To confirm the viability of the diffusion process, planar p-n diodes with a fairly low forward voltage drop ͑3.3 V at 100 A/cm 2 ͒ and high reverse blocking capability ͑more than 1100 V͒ were fabricated. Built-in voltage of 2.9 V, which is typical for 4H-SiC p-n diodes, was obtained by capacitance-voltage measurement.
Investigation of porous silicon carbide layer morphology and its growth rate was studied along with electrical characterization. Morphology of the formed porous SiC layers was analyzed by scanning electron microscopy. The effective carrier density in porous layers was extracted from the capacitance-voltage characteristics of mercury probe Schottky contacts to the porous layer. It was found that the effective carrier density in porous layer and the pore density are in good correlation.The wide bandgap of silicon carbide ͑SiC͒ semiconductor gives it the edge over other materials for making high power, high temperature, and high frequency devices. High thermal conductivity, saturation electric drift velocity, and breakdown electric field adds to its better thermal and electronic properties.In the last few years it has been recognized that nanostructured porous semiconductor networks show interesting optoelectrical properties different from those of bulk semiconductors. These properties are related to the presence of a three-dimensional ͑3-D͒ interfacial structure with a huge internal surface area and huge volume density of surface-localized electrons. At present, extensive research is devoted to nanostructured semiconductor networks. It is believed that such networks will play an important role in future ͑opto-͒ electronic devices ͑solar cells, light emitting diodes, chemical sensors, electrochromic devices, single electron transistors͒.In recent years, porous silicon carbide has been of interest due to its more efficient luminescence compared to bulk SiC. 1 Also, electroluminescent and gas sensor devices based on porous SiC have been demonstrated. 2,3 In order to use porous SiC in device application, the correlation between electrical characteristics and structural morphology of the porous layer must be understood. The goal of this work was to investigate the surface and pore morphology of 6H-SiC with respect to the effect of varying current density used during electrochemical anodization. The characterization technique used to study the surface and pore morphology has never been reported before. Preparation and CharacterizationPorous silicon carbide ͑por-SiC͒ samples were prepared using n-6H-SiC (0°8Ј off axis͒ wafers from CREE Research Inc. This wafer was nitrogen doped and had a resistivity of 0.174 ⍀ cm. Photo-assisted electrochemical etching was performed on both the polished silicon-and carbon-terminated faces of the samples using a 150 W mercury ͑Hg͒ lamp and a mixture of hydrofluoric acid ͑HF͒ ͑1͒: ethanol ͑1͒ as electrolyte for a time period of 2-60 min. Prior to turning on the current, the sample arrangement in the Teflon cell was kept under the Hg lamp for 1 min. The counter electrode was a platinum wire positioned about 1 cm from the sample. The applied current density was between 10 and 80 mA/cm 2 . Por-SiC samples were analyzed after ultrasonic cleaning in methanol for 10-20 min. Thicknesses of the porous layers were measured by the cylindrical grove technique. In order to study the porous structure b...
p -type doping of 6H-SiC was implemented by diffusion of boron at temperatures higher than 1900 °C. The doping profiles were clearly divided into steep (zone I) and long-tail (zone II) regions. The boron diffusions in both regions are well fitted by erfc functions but with different diffusion coefficients, which are an activation energy (EA) of 6.1 eV and a prefactor (D0) of 3.2 cm2/s for zone I and 4.6 eV and 0.1 cm2/s for zone II, respectively. Further, it has been confirmed that the boron acceptors in zone I are primarily located at shallow energy levels (∼300 meV) and the ones in zone II are located at deep energy levels (∼700 meV).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.