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.

Plasma damage in p-GaN

Abstract: The effect of Inductively Coupled Plasma H2 or Ar discharges on the breakdown voltage of p-GaN diodes was measured over a range of ion energies and fluxes. The main effect of plasma exposure is a decrease in net acceptor concentration to depths of 400–550 A. At high ion fluxes or energies there can be type conversion of the initially p-GaN surface. Post etch annealing at 900°C restores the initial conductivity.

Structure and dynamics of the Be-H complex in GaAs

Abstract: The symmetry and reorientation kinetics of the Be-H complex in GaAs have been determined in a uniaxial-stress study. The splitting of the 2036 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ vibrational absorption band under stress shows that the complex has trigonal symmetry. The size of the splitting is large and is consistent with a bond-centered position for the H atom, similar to the case of B-H in Si. At temperatures near 120 K the complex can be aligned by an applied stress. A study of the annealing kinetics of the alignment shows that the motion of H from bond-centered site to bond-centered site about the Be acceptor is thermally activated with an energy of 0.37 eV.

Hydride vapor phase epitaxy-grown AlGaN/GaN high electron mobility transistors

Abstract: High quality undoped AlGaN/GaN high electron mobility transistors (HEMTs) structures have been grown by hydride vapor phase epitaxy (HVPE), for the first time. The morphology of the films grown on Al2O3 substrates is excellent, with a root-mean-square roughness of ∼0.2 nm over 10×10 μ m2 measurement area. Capacitance–voltage measurements show the formation of a dense sheet of charge at the AlGaN/GaN interface. This is the first ever report of the formation of a two-dimensional electron gas in a nitride structure grown by HVPE. HEMTs with 1 μm gate length fabricated on these structures show transconductances in excess of 110 mS/mm and drain–source current above 0.6 A/mm.

Investigation of n‐ and p‐type doping of GaN during epitaxial growth in a mass production scale multiwafer‐rotating‐disk reactor

Abstract: n‐ and p‐doped GaN thin films have been epitaxially grown on c‐sapphire substrates by metal‐organic chemical‐vapor deposition in a production scale multiwafer‐rotating‐disk reactor. The in situ doping was performed with material having a low background carrier concentration of n∼mid‐1016 cm−3. Biscyclopentadienyl magnesium (Cp2Mg) and disilane (Si2H6) were used as the precursors for the p and n dopants, Mg and Si, respectively. The effect of mole flow on material, electrical, and optical properties was studied. We observed that both n‐ and p‐type doped GaN exhibited an excellent surface morphology, even with a high mole flow of doping precursors. After the Mg‐doped GaN was annealed in a N2 ambient at ∼700 °C for 30–60 min, the highly resistive GaN was converted into p‐type GaN with a low resistance of 0.1–1.0 Ω cm. Transmission electron microscopy showed that the defect density on the annealed Mg‐doped GaN is only 4×109 cm−2 which is of the same order as undoped GaN (1.5×109 cm−2). One of the best p‐GaN s...

Detection of chloride ions using an integrated Ag∕AgCl electrode with AlGaN∕GaN high electron mobility transistors

Abstract: AlGaN∕GaN high electron mobility transistors (HEMTs) with an Ag∕AgCl gate exhibit significant changes in channel conductance upon exposing the gate region to various concentrations of chloride (Cl−) ion. The Ag∕AgCl gate electrode, prepared by potentiostatic anodization, changes electrical potential when it encounters Cl− ions. This gate potential changes lead to a change of surface charge in the gate region of the HEMT, inducing a higher positive charge on the AlGaN surface, and increasing the piezoinduced charge density in the HEMT channel. These anions create an image positive charge on the Ag gate metal for the required neutrality, thus increasing the drain current of the HEMT. The HEMT source-drain current was highly dependent on Cl− ion concentration. The limit of detection achieved was 1×10−8M using a 20×50μm2 gate sensing area.

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.