Hans L. Hartnagel

Ion implantation as a tool for controlling the morphology of porous gallium phosphide

We investigate the morphology of porous layers obtained by electrochemical anodization of (100)-oriented n-type GaP substrates before and after a preliminary 5-MeV Kr+ implantation. Apart from favoring the observation of a surface-related phonon in the frequency gap between the bulk optical phonons, ion implantation appears to be an effective means of controlling the morphology of porous GaP, irrespective of initial substrate material features.

Porosity-induced modification of the phonon spectrum of n-GaAs

Porous GaAs layers have been produced by anodic etching of (100)-oriented crystalline substrates in a solution. Scanning electron microscope images showed the formation of submicron pores, the average dimension of the remaining GaAs walls being of about 100 nm. Raman scattering by LO-phonon - plasmon coupled modes, inherent in as-grown crystals, was not observed in the porous layers. Proposed explanations are either the depletion of the GaAs skeleton due to the surface space-charge effect or the decoupling of the LO-phonon and the plasmon modes at the relative large wavevectors transferred in nanostructures. A new Raman scattering peak at , located between the bulk TO and LO frequencies, has been observed in porous layers and attributed to a surface-related phonon.

Infrared thermopile sensor based on AlGaAs—GasAs micromachining

Abstract Infrared bolometry is demonstrated using broadband gold black absorbers positioned on micromachined AlGaAs membranes of high thermal resistance. With a cascade of 20 AlGaAs thermocouple, the radiation-induced temperature difference is measured. Black-body radiation in the range of 315–530 K is used to test the sensor and a sensitivity of R = 145 V W -1 and corresponding detectivity of D * = 4.1 × 10 7 cm Hz 1/2 W -1 are reached. The relatively simple technology that is compatible with MESFET technology results in thermopile sensors that are compared to similar sensors fabricated in polysilicon and Biue5f8Sbue5f8Te technologies.

The characteristics of high-resistance layers produced in n-GaAs using MeV-nitrogen implantation for three-dimensional structuring

The radiation damage introduced in n-GaAs by 4-MeV N+ implantation at a dose of 1×1015 cm−2 has been analyzed using micro-Raman spectroscopy. Implantation followed by annealing at 600u2009°C was found to produce a strongly compensated near-surface layer possessing a high crystalline quality. At the same time a pronounced disorder was found underneath the high-resistance layer which enables the fabrication of 2.5-μm thick free-standing membranes using selective electrochemical etching techniques.

Deep implantation of nitrogen into GaAs for selective three‐dimensional microstructuring

Results are presented for deep implantation of nitrogen into n‐type GaAs. The main purpose of these investigations is to clarify whether deep implantation can be a suitable process to create buried, selectively etchable layers for the fabrication of micromechanical structures in GaAs. The implanted layers have been characterized by x‐ray photoelectron spectroscopy (XPS) combined with sputter profiling, electrical measurements using test Schottky diodes, and selected etching techniques. XPS depth profiling shows the formation of a GaAs1−xNy layer with y<x that can be etched with high selectivity with respect to the GaAs using alkaline agents. The degree of radiation damage introduced during implantation is determined by planar test diodes located at different depth levels in the implanted structure. It can be shown that implantation damage recovers to a certain extent after annealing at a temperature of about 750u2009°C although the optimum annealing conditions have not yet been found.

The Scattering Behaviour of Air Bridges in Coplanar MMIC'S

The scattering behaviour of air bridges for coplanar monolithic microwave integrated circuits (MMICs) is investigated using a three-dimensional Finite-Difference method (FDM). Results on the reflection parameters of the coplanar mode and the transmission parameters of the parasitic slot-line mode axe presented.

Vacuum nanoelectronic devices : novel electron sources and applications

Description: Vacuum Nanoelectronic Devices introduces up–to–date coverage of research in electron field emission from nanostructures. It outlines the physics of quantum nanostructures, the basic principles of electron field emission and vacuum nanoelectronic devices operation, and offers an insight into the state–of–the–art and future research and developments. The book also evaluates the results of research and development into novel quantum electron sources, which will determine the future development of vacuum nanoelectronics. Moreover, the influence of quantum mechanical effects on high frequency vacuum nanoelectronic devices is also assessed. Key features: In–depth description and analysis of the fundamentals of quantum electron effects in novel electron sources; Comprehensive and up–to–date summary of the physics and technologies for THz sources for students of physical and engineering specialties and electronics engineers; Unique coverage of quantum physical results for electron–field emission and novel electron sources with quantum effects, relevant for many applications such as electron microscopy, electron lithography, imaging and communication systems and signal processing; New approaches for the realization of electron sources with required and optimal parameters in electronic devices such as vacuum micro and nanoelectronics. This book is an essential reference for researchers working in terahertz technology, who want to expand their knowledge of electron beam generation in vacuum and electron source quantum concepts. It will also be invaluable to advanced students in electronics engineering and physics who want to deepen their understanding of this topic. Ultimately, the progress of the quantum nanostructure theory and technology will promote the progress and development of electron sources as a main part of vacuum macro–, micro– and nanoelectronics.

Process-Induced Defects in InP Caused by Chemical Vapor Deposition of Surface Passivation Dielectrics

Near-surface defects of InP produced during three different chemical vapor deposition (CVD) processes were systematically characterized by capacitance-voltage ( C-V ) and deep level transient spectroscopy (DLTS) techniques. Deposition of plasma-enhanced CVD (PECVD) phosphosilicate glass (PSG) and SiO2 films produced the same bulk level, lying at 0.35 eV below the conduction band edge, near the surface region of InP. Such a level was absent in the samples prepared by the photo CVD process. In addition, the photo CVD process gave a lower density of interface states than the PECVD process. The origin of the bulk trap and the energy- and space-distributed nature of interface states are discussed.

Effect of metallization on crystalline perfection and level of stress in semi-insulating and n-type gallium arsenide single-crystal wafers

Results obtained by x‐ray diffractometry, topography, and curvature measurements made with a quadruple‐crystal x‐ray diffractometer used in (+,−,+) setting and as a Lang system are reported. About 0.1‐mm‐thick semi‐insulating (SI) (Cr‐compensated) and n‐type wafers with dimensions ∼10×10 mm2 or less were used. The metallizations were (i) Ge‐Ni‐WSi2‐Au and (ii) Ge‐Au‐Ni‐WSi2‐Au, with layer thicknesses as follows: Ge: 20 nm; Au: 5 nm; Ni: 10 nm; WSi2: 100 nm; and Au: 100 nm. Both types of metallizations were deposited on n‐type crystals, whereas only the second type was used with SI wafers. Diffraction curve half‐widths of the wafers without deposits were in the range 15–22 arcsec (SI) and 18–30 arcsec (n type). Radii of curvature (R) were around 6 and 3 m for SI and n‐type crystals, respectively. Topographs showed low defect density. Metallization decreased the level of perfection and enhanced curvature. Diffraction curve half‐widths increased up to 155 arcsec (SI) and 180 arcsec (n type). High‐strain fiel...

Studies of GaAs surfaces by scanning tunnelling induced photon emission

Abstract A scanning tunnelling microscope (STM) is used in order to induce photon emission out of technology relevant p and n doped GaAs (100) surfaces. By detecting the emitted light with a photon counting system, the photon map is recorded additionally to the usual topographic image. This technique is used to investigate the influence of surface damage on the emission intensity with nanometer resolution. We could show that the intensity of photon emission depends on the doping type and concentration and also on the surface quality. Surface areas with mechanically induced crystal defects show a drastically reduced luminescence intensity.