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.

SiC via holes by laser drilling

Abstract: Through-wafer vias were formed in 400-µm-thick bulk 4H-SiC substrates by CO2 laser drilling (1.06-µm λ) with a o-switched pulse width of ∼30 nsec and a pulse frequency of 8 Hz. The resultant pulse energy delivered to the SiC surface was on the order of 60 mJ/pulse. Laser drilling produces much higher etch rates (229–870 µm/min) than conventional dry etching (0.2–1.3 µm/min) and the via entry can be tapered to facilitate subsequent metallization. Laser drilling combines optical and mass spectroscopic methods to in-situ monitor and control the laser ablation plume and ionized debris, reducing the total residual surface contamination.

High‐rate, anisotropic dry etching of InP in HI‐based discharges

Abstract: Electron cyclotron resonance HI/H2Ar discharges with additional rf‐induced dc biasing of the sample have been used to obtain extremely anisotropic dry etching of InP. At a fixed ratio of 10 HI/10 H2/5 Ar (total flow rate 25 sccm) and 1 mTorr pressure, both n+ and p+ InP have etch rates of ∼875 A×min−1 at −100 V bias and ∼3000 A min−1 at −400 V bias. The etch rates increase rapidly with total discharge pressure, reaching 4000 A min−1 at 20 mTorr and −100 V dc bias. Rates in excess of 1 μm min−1 are obtained with higher HI flow rates or higher biases. Features 0.5 μm wide and 13 μm high have been etched, demonstrating the promise of this gas chemistry for production of laser mesas on InP and related materials with substantially faster etch rates (typically a factor of 8–10) relative to the more conventional CH4/H2 mixtures. The etched surfaces are smooth, with no evidence for iodine‐containing residues or preferential loss of either In or P. Both photoresist and SiO2 masks show minimal erosion in this mixture because of the ability to obtain practical etch rates at low pressure and low self‐bias.

Optical and magnetic behavior of erbium-doped GaN epilayers grown by metal-organic chemical vapor deposition

Abstract: The authors report on the optical and magnetic properties of GaN epilayers, grown by metal-organic chemical vapor deposition, with in situ Er doping at concentrations up to ∼1021cm−3. Using ultraviolet laser excitation, all samples exhibited photoluminescence near 1540nm with the integrated intensity approximately proportional to the Er concentration. Data from superconducting quantum interference device measurements indicated room temperature ferromagnetic ordering in all Er-doped GaN epilayers. The saturation magnetization in these samples also followed a nearly linear fit to the Er concentration. X-ray diffraction spectra did not reveal evidence of any second phases over this range of Er concentrations.

Point defects controlling non-radiative recombination in GaN blue light emitting diodes: Insights from radiation damage experiments

Abstract: The role of Shockley-Read-Hall non-radiative recombination centers on electroluminescence (EL) efficiency in blue multi-quantum-well (MQW) 436 nm GaN/InGaN light emitting diodes (LEDs) was examined by controlled introduction of point defects through 6 MeV electron irradiation. The decrease in the EL efficiency in LEDs subjected to irradiation with fluences above 5 × 1015 cm−2 was closely correlated to the increase in concentration of Ec-0.7 eV electron traps in the active MQW region. This increase in trap density was accompanied by an increase in the both diode series resistance and ideality factor (from 1.4 before irradiation to 2.1 after irradiation), as well as the forward leakage current at low forward voltages that compromise the injection efficiency. Hole traps present in the blue LEDs do not have a significant effect on EL changes with radiation because of their low concentration.

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.