Compound Semiconductor Structures Research Articles

Spatioselective Growth on Homogenous Semiconductor Substrates by Surface State Modulation.

Nanofabrication schemes usually suffer challenges in direct growth on complex nanostructured substrates. We provide a new technology that allows for the convenient, selective growth of complex nanostructures directly on three-dimensional (3D) homogeneous semiconductor substrates. The nature of the selectivity is derived from surface states modulated electrochemical deposition. Metals, metal oxides, and compound semiconductor structures can be prepared with high fidelity over a wide scale range from tens of nanometers to hundreds of microns. The utility of the process for photoelectrochemical applications is demonstrated by selectively decorating the sidewalls and tips of silicon microwires with cuprous oxide and cobalt oxides catalysts, respectively. Our findings indicate a new selective fabrication concept applied for homogeneous 3D semiconductor substrates, which is of high promise in community of photoelectronics, photoelectrochemistry, photonics, microelectronics, etc.

MOVPE of Group‐III Heterostructures for Optoelectronic Applications

AbstractThe method of metalorganic vapor phase epitaxy (MOVPE) has developed over the recent 50 years into an indispensable tool in research and industrial production for novel compound semiconductor structures and devices. This article provides a brief explanation of its historical development and basic functionality. A major focus will be laid on the growth of group‐III nitride heterostructures which, on the one hand, owing to their unique material properties, impose challenging problems, but, on the other hand, have evolved into the most important semiconductor family just after silicon mainly due to their application in solid‐state lighting, which would not be possible without their successful growth by MOVPE.

(Invited) Chemical and Electronic Surface Structure of Compound Semiconductors for Solar Water Splitting

The purpose of this talk is to utilize a tool chest of soft x-ray and electron spectroscopies (in particular using high-brilliance synchrotron radiation) to gain insights into the electronic and chemical surface properties of candidate materials for solar water splitting. Focus will be placed on GaInP2- and Cu(In,Ga)(S,Se)2-based material systems, and how ambient conditions and deliberate tailoring can modify and impact the surface of such materials. It will be shown that photoelectron spectroscopy (PES), x-ray-excited Auger electron spectroscopy (XAES), inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive band edge positions, band gaps, electronic level alignment, and insights into chemical stability, both with experiments in ultra-high vacuum, as well as under in situ and operando conditions.

Learning physical descriptors for materials science by compressed sensing

The availability of big data in materials science offers new routes for analyzing materials properties and functions and achieving scientific understanding. Finding structure in these data that is not directly visible by standard tools and exploitation of the scientific information requires new and dedicated methodology based on approaches from statistical learning, compressed sensing, and other recent methods from applied mathematics, computer science, statistics, signal processing, and information science. In this paper, we explain and demonstrate a compressed-sensing based methodology for feature selection, specifically for discovering physical descriptors, i.e., physical parameters that describe the material and its properties of interest, and associated equations that explicitly and quantitatively describe those relevant properties. As showcase application and proof of concept, we describe how to build a physical model for the quantitative prediction of the crystal structure of binary compound semiconductors.

LED Production Yield Improvement Using Advanced In Situ Metrology Systems

Optoelectronic compound semiconductor (CS) structures such as LEDs are typically grown in a complex multi-step hetero epitaxial process. Hence close supervision of the tight growth conditions is a must in order to manufacture high quality devices. Differently to the silicon semiconductor industry, CS devices are still manufactured on relatively small substrates. In 2009 nearly 70% of the compound semiconductor devices were still produced on 2" sapphire wafers. In-situ metrology provides real time access to pocket and wafer temperature, growth rate of individual layers and morphology information to eventually control the complex multi-layer growth. By 2015 market researchers predict a lager penetration of 4" and 6" sapphire wafer, which increases the device count per wafer and is expected to reduce manufacturing cost. However, on such larger substrates several wafer bow effects become much more critical for the device performance. Hence, advanced in-situ control of wafer curvature optimization will become mandatory to improve and maintain high production quality and yield.

The complex material properties of chalcopyrite and kesterite thin‐film solar cell absorbers tackled by synchrotron‐based analytics

ABSTRACTIn view of the complexity of compound semiconductor based thin‐film solar cells, which are comprised of a multitude of layers, interfaces, surfaces, elements, impurities, etc., it is crucial to characterize and understand the structural, chemical, and electronic properties of these components. Hence, this paper gives a review of our recent progress in the characterization of compound semiconductor thin films using synchrotron‐based characterization methods. It is demonstrated how different analytical techniques are extraordinarily powerful to reveal the material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of these properties. Light will be shed on structural phase transitions, reactive thin‐film formation mechanisms, surface off‐stoichiometries, and the electronic structure of chalcopyrite and kesterite compound semiconductors. Copyright © 2012 John Wiley & Sons, Ltd.

Wafer‐Scale Strain Engineering of Ultrathin Semiconductor Crystalline Layers

The fabrication of a wafer-scale dislocation-free, fully relaxed single crystalline template for epitaxial growth is demonstrated. Transferring biaxially-strained Inx Ga1-x As ultrathin films from InP substrates to a handle support results in full strain relaxation and the Inx Ga1-x As unit cell assumes its bulk value. Our realization demonstrates the ability to control the lattice parameter and energy band structure of single layer crystalline compound semiconductors in an unprecedented way.

Sputtering Behavior and Evolution of Depth Resolution upon Low Energy Ion Irradiation of GaAs

We investigate the sputtering behavior and depth resolution upon low energy ion irradiation during Secondary Ion Mass Spectrometry (SIMS) depth profiling of GaAs. We present a systematic and quantitative study of the impact of ion species, primary ion impact energy, and incident angle on the evolution of depth resolution, using a well-defined InGaAs/GaAs multilayer structure with highly abrupt hetero-interfaces. We demonstrate that for low energy O2+ ion beam irradiation, SIMS depth resolution becomes progressively degraded by (transient) incorporation of high surface O-concentration levels in the altered layer, leading to detrimental ion-beam induced formation of topography. In case of low energy oblique Cs+ ion beam irradiation, sputtering behavior of GaAs is well-behaved with no significant transient yield changes and a constant depth resolution. This enables SIMS depth profiling of sharp hetero-epitaxial III-V compound semiconductor structures and shallow dopant profiles with sufficiently good depth resolution with good detection efficiency.

6th International Workshop on Expert Evaluation & Control of Compound Semiconductor Materials & Technologies

The EXMATEC workshops are a series of biannial conferences with the aim to bring together research and development specialists involved in compound semiconductor material physics, chemistry, process technology, characterization and device fabrication. EXMATEC 2002 is the continuation of successful meetings, previously held in Lyon, Parma, Freiburg, Cardiff and Heraklion. The central topics were development, improvement and application of new and advanced methods in the fabrication and evaluation of compound semiconductor materials and structures to develop understanding of the interrelationship between structural, electrical and other material properties and device characteristics, such as performance, reliability, reproducibility, lifetime, yield, etc. The conference topics apply to all compound semiconductor materials (III–V, II–VI, IV–IV, II–IV–V2), related structures and processing steps (from substrate and epitaxial growth to complete devices) and cover instrumentation and characterization issues. The full Proceedings of EXMATEC 2002 are published in the second issue of the new journal series physica status solidi – conferences Vol. 0, No. 2 (2003). As one representative example of the topics presented at this conference, the cover picture of the present issue issue of phys. stat. sol. (a) shows the band scheme of a typical GaInAs/AlInAs superlattice quantum cascade laser, taken from the invited paper by Razeghi and Slivken [1].

Thermodynamic analysis of anion exchange during heteroepitaxy

A thermodynamic approach is presented to assess the extent of anion exchange reactions during the heteroepitaxy (molecular beam epitaxy) of dissimilar anion III–V compound semiconductor structures. It is shown that the extent of anion exchange can be predicted by the change in the Gibbs free energy. Bond strength changes can only be used as a guide in comparing the relative tendency for exchange, rather than as a criterion. The driving force for anion exchange strongly depends on the conditions during interface formation. A number of important factors, including bond strength, misfit strain energy, surface structure and energy, the equilibrium between dimers V 2 and tetramers V 4, and segregation are discussed in terms of their contributions to the thermodynamics.

Charge shift as a criterion of correctness of the surface electronic structure LCAO calculations

An essential problem in semiempirical LCAO calculations of the surface electronic structure of compound semiconductors is the dependence of the results on the values of Hamiltonian parameters. To be more specific, various sets of Hamiltonian parameters, equally well reproducing the dispersion curves and the main band gap of crystal volume, lead to differences in the surface-state dispersion curves which, in turn, influence the Fermi level position. As an example, the (001) surface of a strongly ionic β-GaN semiconductor is considered. On the basis of the obtained results, it is suggested that the value of a charge shift can be used as an additional criterion of the correctness of Hamiltonian parametrization.

Slip in GaAs substrates during molecular beam epitaxial growth:an X-ray topographic survey

Synchrotron X-ray transmission topography has been used to study different types of dislocation bundle in 2-inch diameter, (0 0 1) oriented GaAs substrates after growth of a variety of heteroepitaxial III–V compound semiconductor structures. The dislocation bundles of the majority type start at the sample edges in regions of up to about ±25° around the four 〈1 0 0〉 peripheral areas, glide typically up to about 1.5 cm into the bulk of the wafer following ±[1 1 0] and ± [1 1 ̄ 0] line directions and form, depending on the dopant type, pseudo-symmetric four- or two-fold sets. The dislocation bundles were observed in samples that were grown in three different makes of molecular beam epitaxy machine. Eradication of the bundles was achieved by modifications to the sample holder of an MBE machine built at the Defence Evaluation and Research Agency, Great Malvern, UK.

Makyoh topography for the morphological study of compound semiconductor wafers and structures

The application of Makyoh topography in the assessment of flatness and overall curvature of semiconductor wafers and layer structures is reviewed, with special emphasis on compound semiconductors. Application examples are shown as well.

Electrical characterization of semiconductor materials and devices using scanning probe microscopy

Several scanning probe microscopy (SPM) modes exist for the electrical characterization of semiconductor materials and devices with nm-scale resolution. The most important electrical SPM modes are: scanning capacitance microscopy (SCM), scanning spreading resistance microscopy (SSRM), and tunneling-AFM (TUNA). SCM and SSRM are primarily used for 2-D carrier profiling and resistivity mapping on cross-sectioned devices. The spatial resolution is on the order of 20nm, while the dynamic range goes from 1015 to 1020atoms/cm3. Imaging examples are shown for sub-quarter micron MOSFETs, ferro-electric material, and compound semiconductor structures. The TUNA method allows one to perform thickness mapping and defect imaging of thin dielectric films using a tunneling current flowing between the SPM tip and the sample. Spatial resolution is on the nm-scale, while the current range is from 50fA to 120pA. Examples are shown of gate oxide breakdown and defect localization in thin gate oxides.

Photoresponse on Surface Acoustic Wave Devices with Compound Semiconductor and LiNbO3 Structures

We studied the photoresponse on a surface acoustic wave (SAW) device coupled with AlGaAs film. The experimental results indicate that the transferred carriers by SAW are optically generated electrons rather than optically generated holes. The electric field due to SAW propagation reduces the recombination of the optically generated electrons and holes. We were able to observed a modulated SAW signal due to the nonlinear interaction between SAW and optically induced carriers. The photoresponse due to the interaction between SAW and optically induced carriers shows a high sensitivity for the light intensity. The main results are (1) the control of SAW by optically induced carriers, and (2) the control of the optically induced carriers by SAW. We expect that the characteristics of the photoresponse will be applicable to the fabrication of functional optical-SAW coupled devices.

Why Can Smart Cut® Change the Future of Microelectronics?

Deposition techniques like chemical vapor deposition (CVD) offer to the semiconductor industry the initial flexibility to deposit thin films of key materials on many kinds of substrates. The homoepitaxy or hetroepitaxy techniques using CVD or molecular beam epitaxy (MBE) add the flexibility to get a pure monocrystalline thin film but with a major limitation: the starting substrate has to be monocrystalline. The missing technology has always been the one which allows the growth of a thin monocrystalline film on any kind of substrate. Hydrogen induced splitting (known today as Smart Cut®), discovered at the LETI laboratory in 1991, provides a unique opportunity to get crystalline layers on any kind of substrate. Therefore, a new tool is offered to the semiconductor industry, for new material developments and new structures. This technique is in use in production today on a first application: silicon-on-insulator (SOI) wafers which consist of a monocrystalline film of silicon on a thin amorphous silicon dioxide layer, on top of a silicon wafer. We will discuss the SOI application of the Smart Cut® technology and present other recently demonstrated breakthroughs in new material development, including SiC, compound semiconductor or 3D structures.

WHY CAN SMART CUT® CHANGE THE FUTURE OF MICROELECTRONICS?

Deposition techniques like chemical vapor deposition (CVD) offer to the semiconductor industry the initial flexibility to deposit thin films of key materials on many kinds of substrates. The homoepitaxy or hetroepitaxy techniques using CVD or molecular beam epitaxy (MBE) add the flexibility to get a pure monocrystalline thin film but with a major limitation: the starting substrate has to be monocrystalline. The missing technology has always been the one which allows the growth of a thin monocrystalline film on any kind of substrate. Hydrogen induced splitting (known today as Smart Cut®), discovered at the LETI laboratory in 1991, provides a unique opportunity to get crystalline layers on any kind of substrate. Therefore, a new tool is offered to the semiconductor industry, for new material developments and new structures. This technique is in use in production today on a first application: silicon-on-insulator (SOI) wafers which consist of a monocrystalline film of silicon on a thin amorphous silicon dioxide layer, on top of a silicon wafer. We will discuss the SOI application of the Smart Cut® technology and present other recently demonstrated breakthroughs in new material development, including SiC, compound semiconductor or 3D structures.

Sublattice reversal epitaxy: a novel technique for fabricating domain-inverted compound semiconductor structures

Sublattice reversal in III–V compound semiconductors grown on group-IV epitaxial layers on III–V substrates has been proposed for fabricating nonlinear optical devices with domain-inverted compound semiconductor structures. Sublattice reversal epitaxy has been demonstrated in GaAs/Si/GaAs, GaP/Si/GaP, and GaAs/Ge/GaAs systems. Growth of sublattice-reversed epilayers is assisted by selfannihilation of antiphase domains. Periodically domain-inverted AlGaAs waveguides of satisfactorycrystal quality have been successfully fabricated using sublattice reversal epitaxy of GaAs/Ge/GaAs (100) system combined with photolithography and regrowth techniques.

New Scanning Photoluminescence Technique for Quantitative Mapping the Surface Recombination Velocity in InP and Related Materials

This paper introduces a new approach, based on room temperature (RT) scanning photoluminescence (SPL) measurements, for non-destructive quantitative mapping of the surface or interface recombination velocity in compound semiconductor structures. The developed technique is validated and applied here to spatially resolved evaluation of the surface recombination velocity of InP substrates and InGaAs(C)/InP heterostructures.

One-dimensional photonic bandgap microcavities for strong optical confinement in GaAs and GaAs/Al/sub x/O/sub y/ semiconductor waveguides

Photonic bandgap (PBG) waveguide microcavities with tightly confined resonant optical modes have been designed, fabricated using high-dielectric-contrast GaAs/Al/sub x/O/sub y/ III-V compound semiconductor structures, and characterized optically. The photonic crystal lattices are defined by one-dimensional (1-D) arrays of holes in waveguides, and a controlled defect in the spacing between two holes of an array defines a microcavity. Waveguide microcavity resonances have been studied in both monorail and suspended air-bridge geometries. Resonance states with cavity Q's as high as 360 were measured at wavelengths near 1.55 /spl mu/m, with modal volumes as small as 0.026 /spl mu/m, which corresponds to only two times (/spl lambda//2n)/sup 3/.