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.

Ferromagnetism in Transition-Metal Doped ZnO

Abstract: ZnO is an attractive candidate for spintronics studies because of its potential for exhibiting high Curie temperatures and the relative lack of ferromagnetic second phases in the material. In this paper, we review experimental results on transition-metal (TM) doping of ZnO and the current state of theories for ferromagnetism. It is important to re-examine some of the earlier concepts for spintronics devices, such as the spin field-effect transistor, to account for the presence of the strong magnetic field that has deleterious effects. In some of these cases, the spin device appears to have no advantage relative to the conventional charge-control electronic analog. We have been unable to detect optical spin polarization in ZnO.

Fast electrical detection of Hg(II) ions with AlGaN∕GaN high electron mobility transistors

Abstract: Bare Au gated and thioglycolic acid functionalized Au-gated AlGaN∕GaN high electron mobility transistors (HEMTs) were used to detect mercury (II) ions. Fast detection of less than 5s was achieved for thioglycolic acid functionalized sensors. This is the shortest response time ever reported for mercury detection. Thioglycolic acid functionalized Au-gated AlGaN∕GaN HEMT based sensors showed 2.5 times larger response than bare Au-gated based sensors. The sensors were able to detect mercury (II) ion concentration as low as 10−7M. The sensors showed an excellent sensing selectivity of more than 100 for detecting mercury ions over sodium or magnesium ions. The dimensions of the active area of the sensor and the entire sensor chip are 50×50μm2 and 1×5mm2, respectively. Therefore, portable, fast response, and wireless based heavy metal ion detectors can be realized with AlGaN∕GaN HEMT based sensors.

GaN electronics for high power, high temperature applications

Abstract: A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN heterojunction bipolar transistors and GaN metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

Plasma and wet chemical etching of In0.5Ga0.5P

Abstract: Dry and wet chemical etching of epitaxial In0, 5Ga0.5P layers grown on GaAs substrates by gas-source molecular beam epitaxy have been investigated. For chlorine-based dry etch mixtures (PCl3/Ar or CC12F2/Ar) the etching rate of InGaP increases linearly with dc self-bias on the sample, whereas CH4/H2-based mixtures produce slower etch rates. Selectivities of ≥500 for etching GaAs over InGaP are obtained under low bias conditions with PCl3/Ar, but the surface morphologies of InGaP are rough. Both CC12F2/Ar and CH4/H2/Ar mixtures produce smooth surface morphologies and good (≥10) selectivities for etching GaAs over InGaP. The wet chemical etching rates of InGaP in H3PO4:HC1:H2O mixtures has been systemically measured as a function of etch formulation and are most rapid (∼1 μn · min−1) for high HCl compositions. The etch rate,R, in a 1:1:1 mixture is thermally activated of the formR ∝ $$e^{ - E_a /kT} $$ , whereE a = 11.25 kCal · mole−1. This is consistent with the etching being reaction-limited at the surface. This etch mixture is selective for InGaP over GaAs.

Vibrational characteristics of acceptor‐hydrogen complexes in silicon

Abstract: Acceptor‐hydrogen complexes for the group III acceptors, B, Al, and Ga, in Si have been studied with low‐temperature infrared spectroscopy. The Si‐H stretching band narrows dramatically upon cooling to low temperature thereby aiding the detection of the vibrations of the Al and Ga acceptor‐H complexes. The frequency 2201 cm−1 we have measured for the Al‐H complex is in reasonable agreement with the prediction made by G. G. DeLeo and W. B. Fowler [Phys. Rev. B 31, 6861 (1985)] (2220 cm−1 for a 〈111〉 interstitial configuration for the H). Assignment of the new vibrational bands is confirmed by isotopic substitution. The strength of the absorption provides evidence that the passivation is not the result of compensation alone and that a major fraction of the passivated acceptors result in acceptor‐H complexes. A new, low‐energy excitation of the acceptor‐hydrogen complexes gives rise to a sideband to the main stretching vibration and explains the pronounced energy shift and narrowing of the spectra upon cooli...

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.