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.

GaN-based light-emitting diodes on graphene-coated flexible substrates

Abstract: We demonstrate GaN-based thin light-emitting diodes (LEDs) on flexible polymer and paper substrates covered with chemical vapor deposited graphene as a transparent-conductive layer. Thin LEDs were fabricated by lifting the sapphire substrate off by Excimer laser heating, followed by transfer of the LEDs to the flexible substrates. These substrates were coated with tri-layer graphene by a wet transfer method. Optical and electrical properties of thin laser lift-offed LEDs on the flexible substrates were characterized under both relaxed and strained conditions. The graphene on paper substrates remained conducting when the graphene/paper structure was folded. The high transmittance, low sheet resistance and high failure strain of the graphene make it an ideal candidate as the transparent and conductive layer in flexible optoelectronics.

Effects of ultraviolet illumination on dry etch rates of NiFe-based magnetic multilayers

Abstract: NiFe and NiFeCo were dry etched in inductively coupled plasma Cl2/Ar and CO/NH3 discharges, either with or without concurrent UV illumination from a Hg arc lamp. No enhancement was observed for CO/NH3 etching of the two materials, or for Cl2/Ar etching of NiFe. However, enhancements in etch rate of up to a factor of three were observed for Cl2/Ar etching of NiFeCo when ultraviolet (uv) illumination was employed. The etched surface morphologies were similar both with and without the UV irradiation. The etch rates in Cl2/Ar discharges were strongly correlated with the amount of chlorinated residues detected on the surface by Auger electron spectroscopy, indicating that the desorption of the metal chloride reaction products was the rate-limiting step in the etching.

Deep level effects in silicon and germanium after plasma hydrogenation

Abstract: Deep level electron and hole trapping states are observed in n-and p-type silicon after plasma hydrogenation at 250 - 300°C. These defect states are not observed after exposure to a helium plasma. In contrast to these results, no hydrogen or helium plasma-induced levels are seen in n-or p-type germanium after similar heat treatment of up to 600°C. However, hydrogenation of p-type germanium at 600°C significantly enhances the solubility of the rapidly diffusing impurity copper, compared to untreated material. Reproducing the experiments using a helium plasma does not affect the copper solubility. A simple model which accounts for the experimental results is proposed.

Extraction of Migration Energies and Role of Implant Damage on Thermal Stability of Deuterium in Ga2O3

Abstract: Deuterium was incorporated in bulk single crystal β-Ga2O3 samples by either ion implantation (100 keV, 1015 cm−2) or plasma exposure (up to 270°C, 30 mins) of single-crystal β-Ga2O3 and then its stability was examined as a function of annealing temperature. The mechanisms in both cases were extracted by fitting the experimental depth profiles using models within the Florida Object Oriented Process Simulator (FLOOPS) code. In the case of incorporation by implantation, annealing causes the deuterium to migrate toward the surface with simultaneous trapping at the residual implant damage. In the case of plasma incorporation where there is no residual damage, annealing causes outgassing of the deuterium from the surface, mediated through molecule formation. Very good fits to the experimental data are achieved by integrating physics of the outdiffusion mechanisms into the FLOOPS code. The rate constants and diffusivities used for the simulation were found to follow an Arrhenius dependence, with an activation energy for outdiffusion of deuterium of 1.22 eV and 2.58 eV for the release rate of deuterium from trap sites in the implanted case.

High temperature rapid thermal annealing of InP and related materials

Abstract: There are a number of processing steps in which the In-based III–V semiconductors must be heated to temperatures in excess of their incongruent evaporation point. These include implant activation annealing, in situ heating for surface cleaning or contact sintering and growth of epitaxial layers, although in this latter case an overpressure of P, As or Sb vapor should be present. While much attention has been focused on surface preservation during implant activation annealing, there has been less effort on characterizing the surface after other heating steps. In this paper, we will detail some of the characteristics associated with high temperature heating of InP and related compounds.

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.