Stephen J. Pearton

Bio: Stephen J. Pearton is an academic researcher from University of Florida. The author has contributed to research in topics: Dry etching & Etching (microfabrication). The author has an hindex of 104, co-authored 1913 publications receiving 58669 citations. Previous affiliations of Stephen J. Pearton include Kyungpook National University & University of Southern California.

c-erbB-2 sensing using AlGaN∕GaN high electron mobility transistors for breast cancer detection

Abstract: Antibody-functionalized, Au-gated AlGaN∕GaN high electron mobility transistors (HEMTs) were used to detect c-erbB-2, which is a breast cancer marker. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN∕GaN HEMT drain-source current showed a rapid response of less than 5s when target c-erbB-2 antigen in a buffer at clinically relevant concentrations was added to the antibody-immobilized surface. We could detect a range of concentrations from 16.7to0.25μg∕ml. These results clearly demonstrate the promise of portable electronic biological sensors based on AlGaN∕GaN HEMTs for breast cancer screening.

300°C GaN/AlGaN Heterojunction Bipolar Transistor

Abstract: A GaN/AlGaN heterojunction bipolar transistor has been fabricated using Cl2/Ar dry etching for mesa formation. As the hole concentration increases due to more efficient ionization of the Mg acceptors at elevated temperatures (> 250°C), the device shows improved gain. Future efforts should focus on methods for reducing base resistance, which are briefly summarized.

Hydrogen-sensitive GaN Schottky diodes

Abstract: Pt/n-GaN and Pd/n-GaN Schottky diodes were characterized for their response to hydrogen as a function of measurement temperature. Even at modest temperatures (80–140 °C), an 80 μm diameter diode shows a large increase (⩾0.5 mA) in forward current upon introduction of ∼10% H2 into a N2 ambient. The change in current increases with measurement temperature and begins essentially immediately upon introduction of the hydrogen. Cycling the ambient from N2 to 10% H2 in N2 and back to N2 produces reproducible cycling of the forward current at fixed forward bias. The decrease in barrier height of Pt on GaN was 50 mV at 25 °C and 70 mV at 150 °C upon introduction of H2 into the ambient, with lower values for Pd. At high temperature, the time response of the sensors appears to be controlled by hydrogen diffusion to the metal/GaN interface, while at low temperatures (<100 °C), dissociation of the gas appears to be the rate-determining step.

Energy band offsets of dielectrics on InGaZnO4

Abstract: Thin-film transistors (TFTs) with channels made of hydrogenated amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) are used extensively in the display industry. Amorphous silicon continues to dominate large-format display technology, but a-Si:H has a low electron mobility, μ ∼ 1 cm2/V s. Transparent, conducting metal-oxide materials such as Indium-Gallium-Zinc Oxide (IGZO) have demonstrated electron mobilities of 10–50 cm2/V s and are candidates to replace a-Si:H for TFT backplane technologies. The device performance depends strongly on the type of band alignment of the gate dielectric with the semiconductor channel material and on the band offsets. The factors that determine the conduction and valence band offsets for a given material system are not well understood. Predictions based on various models have historically been unreliable and band offset values must be determined experimentally. This paper provides experimental band offset values for a number of gate dielectrics on IGZO for nex...

Electrical and optical properties of Fe-doped semi-insulating GaN templates

Abstract: Electrical and optical properties of semi-insulating GaN films with the lower part of the film doped with Fe were studied. The room-temperature sheet resistivity of the films was found to be 2×1010 Ω/square. The activation energy of the dark conductivity was ∼0.5 eV which corresponds to the depth of the dominant electron traps pinning the Fermi level. The concentration of these traps was highest in the Fe-doped portion of the films and was on the order of 3×1016 cm−3. Photoinduced current transient spectroscopy also showed the presence of a high concentration of deeper electron traps with level at EC−0.9 eV and hole traps at EV+0.9 eV. These layers look very promising as insulating buffers for AlGaN/GaN transistor structures.

A comprehensive review of zno materials and devices

Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

Spintronics: Fundamentals and applications

Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

Graphene-based composites

Abstract: Graphene has attracted tremendous research interest in recent years, owing to its exceptional properties. The scaled-up and reliable production of graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), offers a wide range of possibilities to synthesize graphene-based functional materials for various applications. This critical review presents and discusses the current development of graphene-based composites. After introduction of the synthesis methods for graphene and its derivatives as well as their properties, we focus on the description of various methods to synthesize graphene-based composites, especially those with functional polymers and inorganic nanostructures. Particular emphasis is placed on strategies for the optimization of composite properties. Lastly, the advantages of graphene-based composites in applications such as the Li-ion batteries, supercapacitors, fuel cells, photovoltaic devices, photocatalysis, as well as Raman enhancement are described (279 references).

Fundamentals of zinc oxide as a semiconductor

Abstract: In the past ten years we have witnessed a revival of, and subsequent rapid expansion in, the research on zinc oxide (ZnO) as a semiconductor. Being initially considered as a substrate for GaN and related alloys, the availability of high-quality large bulk single crystals, the strong luminescence demonstrated in optically pumped lasers and the prospects of gaining control over its electrical conductivity have led a large number of groups to turn their research for electronic and photonic devices to ZnO in its own right. The high electron mobility, high thermal conductivity, wide and direct band gap and large exciton binding energy make ZnO suitable for a wide range of devices, including transparent thin-film transistors, photodetectors, light-emitting diodes and laser diodes that operate in the blue and ultraviolet region of the spectrum. In spite of the recent rapid developments, controlling the electrical conductivity of ZnO has remained a major challenge. While a number of research groups have reported achieving p-type ZnO, there are still problems concerning the reproducibility of the results and the stability of the p-type conductivity. Even the cause of the commonly observed unintentional n-type conductivity in as-grown ZnO is still under debate. One approach to address these issues consists of growing high-quality single crystalline bulk and thin films in which the concentrations of impurities and intrinsic defects are controlled. In this review we discuss the status of ZnO as a semiconductor. We first discuss the growth of bulk and epitaxial films, growth conditions and their influence on the incorporation of native defects and impurities. We then present the theory of doping and native defects in ZnO based on density-functional calculations, discussing the stability and electronic structure of native point defects and impurities and their influence on the electrical conductivity and optical properties of ZnO. We pay special attention to the possible causes of the unintentional n-type conductivity, emphasize the role of impurities, critically review the current status of p-type doping and address possible routes to controlling the electrical conductivity in ZnO. Finally, we discuss band-gap engineering using MgZnO and CdZnO alloys.