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.

Interaction of Be and O in GaAs

Abstract: Oxygen implanted at a concentration above that of the acceptors in p‐type GaAs is shown to create thermally stable, high‐resistivity material only in the case of Be doping in the GaAs. The effect is not seen for Mg, Zn, or Cd doping. Similarly, there is no apparent interaction of O with n‐type dopants (S or Si) in our measurements. The Be‐O complex in p‐type GaAs is a deep donor, creating material whose sheet resistivity shows an apparent thermal activation energy of 0.59 eV for a structure involving a thin layer (5000 A) of oxygen compensated, Be‐doped GaAs on a semi‐insulating substrate.

Hydrogen plasma passivation effects on properties of p-GaN

Abstract: The effects of hydrogen on the electrical and optical properties of p-GaN were investigated. Hydrogen is readily incorporated into the material at temperatures of 250–350 °C, which is consistent with the low activation energy for diffusion reported by Seager et al. [J. Appl. Phys. 92, 7246 (2002)] in GaN p-n junctions. From comparison with the results of earlier experiments, hydrogen diffusivity appears to be a strong function of the hydrogen concentration incorporated into the material during growth. More than an order of magnitude decrease in hole concentration was observed after the hydrogen plasma treatment and from the measurements of the temperature dependence of conductivity. This is the result of hydrogen passivation of acceptors rather than of increased compensation by donor centers. Hydrogen treatment was also shown to lead to a strong suppression of 0.3 eV and 0.6 eV traps and to a strong increase in the magnitude of the photocurrent which are the results of passivation of deep-level defects by...

Comparison of neutron irradiation effects in AlGaN/AlN/GaN, AlGaN/GaN, and InAlN/GaN heterojunctions

Abstract: Neutron irradiation effects were compared for AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with Al composition in the AlGaN barrier ranging from 20% to 50%, “standard” Al0.25Ga0.75N/GaN HEMTs and for InAlN/GaN HEMTs with InAlN barrier lattice matched to GaN (17% In in the barrier). These samples were exposed to fast reactor neutrons with average energy ∼2 MeV and fluence of 1–3 × 1015 cm−2. The main effect of irradiation was the decrease of two-dimensional electron gas (2DEG) mobility and a positive shift in the threshold voltage corresponding to 2DEG depletion in capacitance–voltage characteristics. For the highest fluences, there was a decrease in both 2DEG concentration and accumulation capacitance, with the effect being strongest for AlGaN/AlN/GaN HEMTs with the highest Al composition and for InAlN/GaN HEMTs. The results correlate with the increase in concentration of deep negatively charged traps in the AlGaN or InAlN barrier with neutron dose. For applications in which tolerance...

Thermal stability of 2H-implanted n- and p-type GaN

Abstract: Implantation of 2H+ into n- and p-type GaN creates high resistivity material in which the resistance displays activation energies of 0.8 and 0.9 eV, respectively. Annealing at 500 °C restores the initial, preimplanted resistance of the n-GaN, due to removal of the deep trap states created by the ion stopping. By contrast, in p-type GaN annealing at 500 °C produces motion of the implanted deuterium and formation of Mg–H complexes that keep the resistance high. About 20% of the deuterium remains in n-GaN even after annealing at 1200 °C, where it decorates the residual implant damage. In p-type GaN all of the deuterium is evolved from the crystal by 1000 °C.

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.