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.

Redistribution and activation of implanted S, Se, Te, Be, Mg, and C in GaN

Abstract: A variety of different possible donor and acceptor impurities have been implanted into GaN and annealed up to 1450 °C. S+ and Te+ produce peak electron concentrations ⩽5×1018 cm−3, well below that achievable with Si+. Mg produces p-type conductivity, but Be+- and C+- implanted samples remained n type. No redistribution was observed for any of the implanted species for 1450 °C annealing. Much more effective damage removal was achieved for 1400 °C annealing of high-dose (5×1015 cm−2) Si+ implanted GaN, compared to the more commonly used 1100 °C annealing.

Valence band offsets for CuI on (-201) bulk Ga2O3 and epitaxial (010) (Al0.14Ga0.86)2O3

Abstract: Thin films of copper iodide (CuI) were grown on (-201) bulk Ga2O3 and (010) epitaxial (Al0.14Ga0.86)2O3 using a copper film iodination reaction method. The valence band offsets for these heterostructures were measured by X-ray photoelectron spectroscopy (XPS). High resolution XPS data of the O 1s peak and onset of elastic losses were used to establish the (Al0.14Ga0.86)2O3 bandgap to be 5.0 ± 0.30 eV. The valence band offsets were −0.25 eV ± 0.07 eV and 0.05 ± 0.02 eV for CuI on Ga2O3 or (Al0.14Ga0.86)2O3, respectively. The respective conduction band offsets were 1.25 ± 0.25 eV for Ga2O3 and 1.85 ± 0.35 eV for (Al0.14Ga0.86)2O3. Thus, there is a transition from type-II to type-I alignment as Al is added to β-Ga2O3. The low valence band offsets are ideal for hole transport across the heterointerfaces.

Mechanism of high density plasma processes for ion-driven etching of materials

Abstract: We propose a mechanism for ion-driven etching of materials in a high density plasma (>1011 cm−3) system. An inductively coupled plasma (ICP) reactor was used to model the etch mechanism. Ion density and plasma potential were measured with a Langmuir probe and the self-induced dc bias simultaneously recorded. Power density (i.e. ion flux times ion energy) was found to be the most influential factor for predicting the etch rate of ion-driven materials, like dielectrics and III-nitrides, especially when running in a high density plasma (HDP) mode. Power density is also shown to be a function of ion mass, ion density, ion charge, dc bias and plasma potential. The relation between these plasma parameters and power density can be correlated with process parameters such as ICP source power, rf chuck power, chamber pressure and gas flow rate. This correlation was modeled with the aid of a design of experiment (DOE) simulation. We have demonstrated the use of a power density model to explain the mechanism responsible for HDP etching of SiO2, which is one example of a high-bond strength material.

Forward turn-on and reverse blocking characteristics of GaN Schottky and p-i-n rectifiers

Abstract: High voltage GaN Schottky and p-i-n rectifiers have been fabricated on heteroepitaxial layers. The Schottky diodes have reverse blocking voltages around 500 V for vertical devices employing undoped, conducting GaN, whereas these voltages are >3000 V for lateral devices employing resistive GaN. The forward turn-on voltages are ⩾3.5 V for the Schottky rectifiers, with ideality factors of 1.5–2. The dominant current transport mechanism is Shockley–Read–Hall recombination. The p-i-n rectifiers fabricated with conducting i layers also have reverse blocking voltages of ∼500 V, but the forward turn-on voltages are typically ∼5 V. A comparison with the state-of-the-art SiC Schottky and p-i-n rectifiers is also given.

Dissociation of P‐H, As‐H, and Sb‐H complexes in n‐type Si

Abstract: Reverse‐bias annealing of P‐H, As‐H, and Sb‐H pairs in hydrogenated Schottky diodes was used to establish the dissociation energies of these complexes. The annealing kinetics are found to be first order, with the dissociation frequencies thermally activated of the form ν=ν0e−ED/kT. The dissociation energies ED are found to be 1.20±0.05 eV for P‐H, 1.12±0.05 eV for As‐H, and 1.13±0.05 eV for Sb‐H. The relative insensitivity of these values to the actual donor species is consistent with the currently accepted model in which the hydrogen passivates the electrical activity of the donor by attaching to one of the donors Si nearest neighbors at an antibonding interstitial site.

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.