Ashok K. Sood

By Ashok K. Sood, Zhong Lin Wang, Dennis L. Polla, Nibir K. Dhar, Tariq Manzur and A.F.M. Anwar

Part of the book: Optoelectronic Devices and Properties

By Nibir K. Dhar, Ravi Dat and Ashok K. Sood

Part of the book: Optoelectronics

By Ashok K. Sood, Nibir K. Dhar, Dennis L. Polla, Madan Dubey and Priyalal Wijewarnasuriya

Part of the book: Optical Sensors

By Ashok K. Sood, John W. Zeller, Robert A. Richwine, Yash R. Puri, Harry Efstathiadis, Pradeep Haldar, Nibir K. Dhar and Dennis L. Polla

Part of the book: Advances in Optical Fiber Technology

By Roger E. Welser, Ashok K. Sood, Ramesh B. Laghumavarapu, Diana L. Huffaker, David M. Wilt, Nibir K. Dhar and Kimberly A. Sablon

Part of the book: Solar Cells

By Ashok K. Sood, Isaac Lund, Yash R. Puri, Harry Efstathiadis, Pradeep Haldar, Nibir K. Dhar, Jay Lewis, Madan Dubey, Eugene Zakar, Priyalal Wijewarnasuriya, Dennis L. Polla and Michael Fritze

Graphene has amazing abilities due to its unique band structure characteristics defining its enhanced electrical capabilities for a material with the highest characteristic mobility known to exist at room temperature. The high mobility of graphene occurs due to electron delocalization and weak electron–phonon interaction, making graphene an ideal material for electrical applications requiring high mobility and fast response times. In this review, we cover graphene’s integration into infrared (IR) devices, electro-optic (EO) devices, and field effect transistors (FETs) for radio frequency (RF) applications. The benefits of utilizing graphene for each case are discussed, along with examples showing the current state-of-the-art solutions for these applications.

Part of the book: Graphene

By Ashok K. Sood, John W. Zeller, Roger E. Welser, Yash R. Puri, Nibir K. Dhar, Priyalal S. Wijewarnasuriya and Sanjay Krishna

The implementation of strained layer superlattices (SLS) for detection of infrared (IR) radiation has enabled compact, high performance IR detectors and two-dimensional focal plane arrays (FPAs). Since initially proposed three decades ago, SLS detectors exploiting type II band structures existing in the InAs/GaSb material system have become integral components in high resolution thermal detection and imaging systems. The extensive technological progress occurring in this area is attributed in part to the band structure flexibility offered by the nearly lattice-matched InAs/AlSb/Ga(In)Sb material system, enabling the operating IR wavelength range to be tailored through adjustment of the constituent strained layer compositions and/or thicknesses. This has led to the development of many advanced type II SLS device concepts and architectures for low-noise detectors and FPAs operating from the short-wavelength infrared (SWIR) to very long-wavelength infrared (VLWIR) bands. These include double heterostructures and unipolar-barrier structures such as graded-gap M-, W-, and N-structures, nBn, pMp, and pBn detectors, and complementary barrier infrared detector (CBIRD) and pBiBn designs. These diverse type II SLS detector architectures have provided researchers with expanded capabilities to optimize detector and FPA performance to further benefit a broad range of electro-optical/IR applications.

Part of the book: Two-dimensional Materials for Photodetector

By Ashok K. Sood, John W. Zeller, Gopal G. Pethuraja, Roger E. Welser, Nibir K. Dhar and Priyalal S. Wijewarnasuriya

This chapter covers recent advances in the development of nanostructure-based material technologies to benefit next-generation electro-optical (EO) and infrared (IR) sensor and imager applications. Nanostructured materials can now be integrated into a variety of technological platforms, offering novel optoelectrical properties that greatly enhance device performance in many practical applications. Use of novel carbon nanotube (CNT) based materials has enabled new approaches for applying nanostructure design methodologies that can offer enhanced performance for low-cost bolometers for IR detection and imaging applications. We will discuss the development of carbon nanostructure based infrared detectors and arrays, including concepts that will provide high performance, high frame rate, and uncooled microbolometers for mid-wave infrared (MWIR) and long-wave infrared (LWIR) band detection. In addition, nanostructured antireflection (AR) coatings are being developed that significantly enhance transmission over a broad spectrum, providing substantial improvements in device performance compared to conventional thin film AR coatings. These nanostructured AR coatings have been demonstrated over visible to LWIR spectral bands on various substrates. In this chapter, we discuss both theoretical and measured results of these diverse nanostructure technologies to advance sensing performance over a wide range of spectral bands for defense, space, and commercial applications.

Part of the book: Nanorods and Nanocomposites

By Ashok K. Sood, John W. Zeller, Parminder Ghuman, Sachidananda Babu, Nibir K. Dhar, Randy N. Jacobs, Latika S. Chaudhary, Harry Efstathiadis, Samiran Ganguly, Avik W. Ghosh, Sheikh Ziauddin Ahmed and Farjana Ferdous Tonni

High-performance graphene-HgCdTe detector technology has been developed combining the best properties of both materials for mid-wave infrared (MWIR) detection and imaging. The graphene functions as a high mobility channel that whisks away carriers before they can recombine, further contributing to detection performance. Comprehensive modeling on the HgCdTe, graphene, and the HgCdTe-graphene interface has aided the design and development of this MWIR detector technology. Chemical doping of the bilayer graphene lattice has enabled p-type doping levels in graphene for high mobility implementation in high-performance MWIR HgCdTe detectors. Characterization techniques, including SIMS and XPS, confirm high boron doping concentrations. A spin-on doping (SOD) procedure is outlined that has provided a means of doping layers of graphene on native substrates, while subsequently allowing integration of the doped graphene layers with HgCdTe for final implementation in the MWIR photodetection devices. Successful integration of graphene into HgCdTe photodetectors can thus provide higher MWIR detector efficiency and performance compared to HgCdTe-only detectors. New earth observation measurement capabilities are further enabled by the room temperature operational capability of the graphene-enhanced HgCdTe detectors and arrays to benefit and advance space and terrestrial applications.

Part of the book: 21st Century Nanostructured Materials