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.

Fabrication and characteristics of high-speed implant-confined index-guided lateral-current 850-nm vertical cavity surface-emitting lasers

Abstract: Process technology of high-speed implant-apertured index-guide lateral-current-injection top dielectric-mirror quantum-well 850-nm vertical cavity surface-emitting lasers (VCSELs) has been developed. Oxygen and helium implantation for aperture definition and extrinsic capacitance reduction, dielectric mirror formation, p- and n-ohmic contact formation, VCSEL resistance, and thermal analysis were investigated. Employing this technology, GaAs/AlGaAs-based 850-nm VCSELs with small signal modulation bandwidths up to 11.5 Gb/s and an eye diagram generated at 12 Gb/s by a pseudorandom bit sequence of 2/sup 31/-1 were achieved. The bit-error rates were below 10/sup -13/. The threshold current is as low as 0.8 mA for 7-/spl mu/m-diameter current apertures and typical slope efficiencies of 0.45-0.5 mA/mW were obtained.

Hydrogen in crystalline semiconductors: part ii–iii–v compounds

Abstract: The properties of hydrogen in III–V semiconductors are reviewed. Atomic hydrogen is found to passivate the electrical activity of shallow donor and acceptor dopants in virtually all III–V materials, including GaAs, Alx Ga1−x As, InP, InGaAs, GaP, InAs, GaSb, InGaP, AlInAs and AlGaAsSb. The passivation is due to the formation of neutral dopant-hydrogen complexes, with hydrogen occupying a bond-centered position in p-type semiconductors and an anti-bonding site in n-type materials. The dopants are reactivated by annealing at ≤400° C. The neutral hydrogen-dopant complexes have characteristic vibrational bands, around 2000cm−1 for stretching modes and 800cm−1 for wagging modes. Deep levels such as EL2, DX and metallic impurities are also passivated by hydrogen. The diffusivity of hydrogen is high in III–V semiconductors and unintentional incorporation can occur during epitaxial growth, annealing in H2, dry etching, water boiling, wet etching or chemical vapor deposition processes, Surface passivation by (NH4)xS or NH3 plasma treatment is also effective in lowering surface recombination velocities in many III-V semiconductors.

Dry etching and implantation characteristics of III-N alloys

Abstract: The wide-gap nitrides GaN, AIN and InN and their ternary alloys are attracting interest for blue-UV emitters, high temperature electronics and as passivation films for other semiconductors. We review the dry etching chemistries that are found to provide smooth anisotropic pattern transfer in these materials, namely Cl 2 H 2 , BCl 3 or CH 4 H 2 for Al x Ga 1− x N alloys and CH 4 H 2 for In x Ga 1− x N alloys. Microwave enhancement of the discharge is useful for increasing the etch rate at fixed d.c. self-bias. Ar + ion milling rates for the nitrides are typically a factor of 2 lower than for conventional III-Vs such as GaAs and InP. Implant isolation of In x Ga 1− x N shows similar characteristics to GaAs, namely a several orders of magnitude increase in resistance after implantation with moderate doses of F + or O + , followed by a further increase with annealing temperature up to about 500°C as hopping conduction is decreased. Minimal diffusion of most implanted dopants is found up to annealing temperatures of 800°C. Prospects for other process modules, especially wet chemical etching and ohmic contacts, will be discussed.

InGaP/GaAs single- and double-heterojunction bipolar transistors grown by organometallic vapour phase epitaxy

Abstract: InGaP/GaAs single-heterojunction bipolar transistors (HBTs) and double-heterojunction bipolar transistors (DHBTs) grown by organometallic vapour phase epitaxy are reported. A current gain beta =40 was obtained for 90 mu m diameter HBT devices at a base-collector bias of 0 V. The base carbon-doping concentration for the devices was 2*1019 cm-3 and the sheet resistivity ( rho s) of the base layer was 600 Omega / Square Operator . For the DHBTs, a current gain beta =27 was obtained for a base-collector bias of 2 V. The carbon doping concentration in these devices was 8*1018 cm-3 with rho s=1400 Omega / Square Operator . This represents the first successful fabrication of DHBTs for this material system.

Transmission electron microscopy characterization of electrically stressed AlGaN/GaN high electron mobility transistor devices

Abstract: A set of AlGaN/GaN high electron mobility transistor devices has been investigated using step-stress testing, and representative samples of undegraded, source-side-degraded, and drain-side-degraded devices were examined using electron microscopy and microanalysis An unstressed reference sample was also examined All tested devices and their corresponding transmission electron microscopy samples originated from the same wafer and thus received nominally identical processing Step-stressing was performed on each device and the corresponding current–voltage characteristics were generated Degradation in electrical performance, specifically greatly increased gate leakage current, was shown to be correlated with the presence of crystal defects near the gate edges However, the drain-side-degraded device showed a surface pit on the source side, and another region of the same device showed no evidence of damage Moreover, significant metal diffusion into the barrier layer from the gate contacts was also observed, as well as thin amorphous oxide layers below the gate metal contacts, even in the unstressed sample Overall, these observations emphasize that gate-edge defects provide only a partial explanation for device failure

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.