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.

Sb-based semiconductors for low power electronics

Abstract: Sb-based semiconductors incorporating heterostructures of InP, InAs, AlSb, InSb, GaSb, InGaAs, InGaSb, GaAsSb and InGaAsSb can be used for high speed, low power applications such as wide-bandwidth telecommunications for aircraft, satellites, wireless communication, and global positioning systems, as well as thermophotovoltaic cells, THz medical imaging and remote sensing, IR sensors for space exploration, high resolution biomedical spectroscopy and military systems, including security scanners. Sb-based electronic devices such as heterojunction bipolar transistors (HBTs) offer high speed, low power consumption and good breakdown voltages. High electron mobility InAs/AlSb or InSb/AlSb and high hole mobility InGaSb/AlSb quantum well heterostructure field effect transistors (HFETs) have also been widely pursued for THz amplifiers and high speed complementary logic circuits.

Dry etch damage in inductively coupled plasma exposed GaAs/AlGaAs heterojunction bipolar transistors

Abstract: The dc current gain and emitter and base sheet resistance of C-doped GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have been used to measure damage introduced by exposure to Ar inductively coupled plasmas (ICP). As the ICP source power is increased at fixed rf chuck power, the damage-induced changes in device characteristics are reduced due to a reduction in ion energy. Beyond a particular ICP source power (∼1000 W for 50 W rf chuck power), the damage increases due to the increase in ion flux, even though the ion energy is low (<30 eV). These results are a clear demonstration of the advantage of high ion density plasmas for pattern transfer in damage-sensitive minority carrier devices such as HBTs.

Low-resistance smooth-surface Ti/Al/Cr/Mo/Au n-type Ohmic contact to AlGaN/GaN heterostructures

Abstract: A comparative study of the specific contact resistivity and surface morphology of Ti/Al/Ni/Au, Ti/Cr/Mo/Au, and Ti/Al/Cr/Mo/Au metal contact stacks on AlGaN/GaN heterostructures is reported. Compared to the conventional Ti/Al/Ni/Au contact, the Ti/Al/Cr/Mo/Au contact has much smoother surface and achieves minimum specific contact resistivity of 1.1×10−6 Ω cm2. This contact maintains its low contact resistivity after storage at 200 °C for 100 h in N2. The robustness of this contact is attributed to the Cr and Mo layers, which suppress the formation of Al–Au alloys in the contact stack.

Effect of Mg ionization efficiency on performance of Npn AlGaN/GaN heterojunction bipolar transistors

Abstract: A drift-diffusion transport model has been used to examine the performance capabilities of AlGaN/GaN Npn heterojunction bipolar transistors (HBTs). The Gummel plot from the first GaN-based HBT structure recently demonstrated is adjusted with simulation by using experimental mobility and lifetime reported in the literature. Numerical results have been explored to study the effect of the p-type Mg doping and its incomplete ionization in the base. The high base resistance induced by the deep acceptor level is found to be the cause of limiting current gain values. Increasing the operating temperature of the device activates more carriers in the base. An improvement of the simulated current gain by a factor of 2 to 4 between 25 and 300 C agrees well with the reported experimental results. A preliminary analysis of high frequency characteristics indicates substantial progress of predicted rf performances by operating the device at higher temperature due to a reduced extrinsic base resistivity.

Characterization of GaAs and Si by a microwave photoconductance technique

Abstract: A nondestructive microwave photoconductance technique has been employed to investigate the uniformity of electrical transport properties in semi‐insulating, doped, or implanted GaAs. Although the measurement time is increased, the technique is also applicable to Si. A review of the advantages and limitations is discussed and some example applications to a variety of GaAs and Si structures are presented.

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.