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We discuss the quantification of the secondary electron doping contrast in the scanningelectron microscope on 4H-SiC. It has been observed and studied at length mostly on silicon, but noconclusive theoretical model has been proposed yet. Therefore, we propose a simple physical modelthat allows for a quantification of the doping contrast. It is based on the changes in effective ionizationenergy for different doping concentrations and types. For a better agreement between our model andthe experiment, a locally increased temperature of the electron system or separate quasi Fermi levelsfor electrons and holes have to be assumed. A line profile of the sample under investigation is comparedwith a SRIM simulation of the corresponding implant and shows very good agreement.

Si

Wir verlassen nun langsam endgultig den Bereich der Halbleiterei, welcher sich der Haushaltselektronik widmet, und wir kommen damit in das Reich der schonen und sehr esoterischen Physik der zweidimensionalen, eindimensionalen und nulldimensionalen Elektronensysteme bei tiefsten Temperaturen und hochsten Magnetfeldern. Um dort uberleben zu konnen, braucht es aber spezielle Fertigkeiten, denn die primitiven Methoden im ersten Teil dieses Buches sind zwar gut und wichtig zum grundsatzlichen Verstandnis der Probleme, aber wenn Sie mit diesen Methoden hier wirklich etwas ausrechnen wollen, werden Sie wohl nicht weit kommen. Aus diesem Grund werden wir uns jetzt erst einmal mit ein paar numerischen Methoden aufmunitionieren. Wichtig: Die hier gezeigten Methoden funktionieren nur bei primitiven, eindimensionalen Problemen. Real world problems lassen sich damit eher nicht losen. Dennoch erklaren diese Methoden die Ideen, und Sie werden nicht vollig planlos sein, falls Sie sich an einem Institut fur theoretische Halbleiterei um eine Diplomarbeit bewerben wollen.

Um Tunnelprozesse in zweidimensionalen Elektronenensystemen zu studieren braucht es ein geeignetes Testvehikel, und das ist eine Resonante Tunneldiode (RTD). Gehen wir also schrittweise vor, und klettern Dimension fur Dimension nach unten, so lange, bis wir bei den nulldimensionalen Systemen ankommen, und Sie am Ende verstehen konnen, warum ich keine Quantencomputer ausstehen kann. Beginnen wir mit den zweidimensionalen Elektronengasen.

Quantencomputer sind dieser Tage naturlich immer und uberall sehr beliebt, allerdings sollte man sich dringend fragen, warum eigentlich.

Am Ende der beiden Bucher ist nun der Moment gekommen, sich die Frage zu stellen, ob sich die ganze Aktion gelohnt hat.

International audience; Semiconductor–superconductor hybrid systems have outstanding potential for emerging high-performance nanoelectronics and quantum devices. However, critical to their successful application is the fabrication of high-quality and reproducible semiconductor–superconductor interfaces. Here, we realize and measure axial Al–Ge–Al nanowire heterostructures with atomically precise interfaces, enwrapped by an ultrathin epitaxial Si layer further denoted as Al–Ge/Si–Al nanowire heterostructures. The heterostructures were synthesized by a thermally induced exchange reaction of single-crystalline Ge/Si core/shell nanowires and lithographically defined Al contact pads. Applying this heterostructure formation scheme enables self-aligned quasi one-dimensional crystalline Al leads contacting ultrascaled Ge/Si segments with contact transparencies greater than 96%. Integration into back-gated field-effect devices and continuous scaling beyond lithographic limitations allows us to exploit the full potential of the highly transparent contacts to the 1D hole gas at the Ge–Si interface. This leads to the observation of ballistic transport as well as quantum confinement effects up to temperatures of 150 K. Low-temperature measurements reveal proximity-induced superconductivity in the Ge/Si core/shell nanowires. The realization of a Josephson field-effect transistor allows us to study the subgap structure caused by multiple Andreev reflections. Most importantly, the absence of a quantum dot regime indicates a hard superconducting gap originating from the highly transparent contacts to the 1D hole gas, which is potentially interesting for the study of Majorana zero modes. Moreover, underlining the importance of the proposed thermally induced Al–Ge/Si–Al heterostructure formation technique, our system could contribute to the development of key components of quantum computing such as gatemon or transmon qubits

Ohne pn-Ubergange geht in der Elektronik gar nichts. Keine Dioden, keine Transistoren, keine regelbaren Kapazitaten, keine Solarzellen, keine Laser und, am allerschlimmsten, keine Mobiltelefone, keine Computer, keine freizeitorientierten Internetseiten und auch kein Counter-Strike und sonstige Ballerspiele (Hausaufgabe: Mailen Sie mir bitte, welches Computerspiel gerade besonders in ist, damit ich mein Buch up to date halten kann). Sich als Elektrotechniker oder Physiker etwas Halbwissen uber den pn-Ubergang anzueignen, ist also durchaus angebracht.

Der Halbleiterhorror nahert sich dem Hohepunkt, und das ist die Boltzmann-Transportgleichung. Warum mussen wir uns das antun? Die Antwort ist einfach, schuld ist das Institut fur Mikroelektronik. Dort kummert man sich um die Simulation der Kennlinien von Halbleiterbauelementen, und dort geht ohne Boltzmann-Gleichung rein gar nichts.

In den bisherigen Betrachtungen haben wir immer angenommen, dass im ganzen Halbleiter immer nur ein einziges (!) freies Elektron existiert. Das ist kein Scherz, bisher gab es wirklich immer nur ein einziges Elektron in all unseren Betrachtungen, und wir haben trotzdem eine Menge gelernt. In einem richtigen Halbleiter kann man aber nur eher selten von so einer Situation ausgehen, und daher widmet sich dieses Kapitel den folgenden Fragen: Wie viele Energiezustande gibt es im Halbleiterkristall? Wie viele Elektronen sind dort uberhaupt vorhanden? Und schlieslich: Wie viele dieser Elektronen sind freie Elektronen und konnen zur Leitfahigkeit beitragen?

Metastable germanium–tin alloys are promising materials for optoelectronics and optics. Here we present the first electrical characterization of highly crystalline Ge0.81Sn0.19 nanowires grown in a solution-based process. The investigated Ge0.81Sn0.19 nanowires reveal ohmic behavior with resistivity of the nanowire material in the range of ∼1 × 10−4 Ω m. The temperature-dependent resistivity measurements demonstrate the semiconducting behavior. Moreover, failure of devices upon heating to moderate temperatures initiating material degradation has been investigated to illustrate that characterization and device operation of these highly metastable materials have to be carefully conducted.

Beginnen wir mit einem Vergleich aus dem taglichen Leben: Sie gehen in den Biomarkt und kaufen 2 kg klassische Kartoffeln. Dann fahren Sie mit dem Fahrrad nach Hause, gehen in Ihre Kuche, legen die Kartoffeln auf die Waage und stellen zufrieden fest: \(m=2\) kg. Jetzt kommt die quantenmechanische Version dieses Einkaufs: Sie nehmen einen Golddraht (das ist der Biomarkt mit den Kartoffeln), loten diesen auf einen Halbleiter und schutten dann 2 kg quantenmechanische Kartoffeln (Elektronen) per Stromfluss in den Halbleiter aus z. B. GaAs (der Halbleiter ist die Kuche). Im Golddraht haben alle Elektronen die ubliche Elektronenmasse \(m_{0}\). Im Halbleiter (Kuche), so sagt die Waage, ist die Elektronenmasse (Kartoffelmasse) nur noch \(m=0.067\cdot m_{0}\). Ahhh, wie das? Kartoffeldiebstahl, Schadlingsbefall oder Antigravitation? Mitnichten, der Grund ist die Auswirkung der Bandstruktur auf die Elektronen im Kristall. Um dieses zu verstehen, fassen wir kurz unsere bisherigen Erkenntnisse bis zu diesem Punkt zusammen:Na gut, aber komplizierte Bandstrukturen sind nichts fur das einfache Gemut eines Experimentalisten und auserdem sind sie in ihrer rohen Form fur die Berechnung irgendwelcher Dioden- oder Transistorkennlinien ziemlich unpraktisch. Aus diesem Grund wird in der Halbleiterphysik durch gnadenlose Analogiebildung zur klassischen Mechanik (deswegen heist das ja auch Quantenmechanik) immer eine effektive Elektronenmasse verwendet, welche dann in allen Experimenten auch wirklich gemessen wird. In dieser effektiven Elektronenmasse stecken dann alle Auswirkungen der Bandstruktur des jeweiligen Halbleiterkristalls und man kann frohlich so tun, als ware der Halbleiter die perfekte Vakuumdose fur freie Elektronen, die jetzt aber eine andere Masse haben und auch eine andere Dielektrizitatskonstante sehen. Merke: Die effektive Masse ist meist kleiner als die Masse des freien Elektrons.

Der Halbleiterhorror nahert sich dem Hohepunkt, und das ist die Boltzmann-Transportgleichung. Warum mussen wir uns das antun? Die Antwort ist einfach, schuld ist das Institut fur Mikroelektronik. Dort kummert man sich um die Simulation der Kennlinien von Halbleiterbauelementen, und dort geht ohne Boltzmann-Gleichung rein gar nichts. Zukunftige Simulanten sollten jetzt also besser gut aufpassen, alle anderen sollten versuchen, zumindest die Ideen hinter den folgenden Formelwursten zu verstehen.

A large resonance splitting is seen when an in-plane magnetic field is applied in non-magnetic InGaAs/GaAsSb/InGaAs resonant tunneling diodes (RTDs). The peak splitting can be explained in terms of the Rashba effect, which is enhanced by the in-plane acceleration that the electrons suffer under the action of the magnetic field. The Rashba splitting reaches values up to 30 meV for B = 5 T and stands temperatures above T = 180 K. The resonance peak splitting provides a new method to determine the Rashba parameter (α). The measured Rashba parameter in these RTDs range from α = 0.38 eVA to α = 0.78 eVA.

La2O3 grown by atomic layer deposition (ALD) and thermally grown GeO2 are used to establish effective electrical surface passivations on n-type (1 0 0)-Ge substrates for high-k ZrO2 dielectrics, grown by ALD at 250 °C substrate temperature. The electrical characterization of MOS capacitors indicates an impact of the Ge-surface passivation on the interfacial trap density and the frequency dependent capacitance in the inversion regime. Lower interface trap densities can be obtained for GeO2 based passivation even though a chemical decomposition of the oxidation states occur during the ALD of ZrO2. As a consequence the formation of a ZrGeOx compound inside the ZrO2 matrix and a decline of the interfacial GeO2 are observed. The La2O3 passivation provides a stable amorphous lanthanum germanate phase at the Ge interface but also traces of Zr germanate are indicated by X-ray-Photoelectron-Spectroscopy and Transmission-Electron-Microscopy.

In this work, the influence of the tip-geometry and an unusual low frequency behavior in scanning capacitance microscopy is investigated experimentally and theoretically on metal–oxide–semiconductor (MOS) and Schottky type junctions on gallium–arsenide (GaAs). Using a two-dimensional model we find that on Schottky type junctions the electric field around the tip is screened by the surface states and that the essential parameters entering the capacitance versus voltage C(V) characteristics are the doping level and the contact area only. On a MOS-type junction, the electric field from the tip penetrates into the semiconductor and the tip geometry effects are much larger. C(V) spectra are fitted to the experimental data and allowed a quantitative determination of doping levels, oxide thickness, and contact area without moreover calibration measurements. Furthermore, we show that the natural surface depletion field on GaAs generates a permanent minority carrier accumulation around the tip–apex. In contrast to thermally generated minority carriers in the space charge region of a large area device, the minority carrier distribution around the SCM tip–apex is detected up to much higher excitation frequencies. An analytic approach to estimate the transition frequency between the low and high frequency regime is also given.

In this work, we present a scheme for room temperature detection of single subsurface InAs quantum dots buried in GaAs by Atomic Force Microscopy based local photocurrent spectroscopy. The measurements were performed at room temperature and ambient conditions. The AFM was used as a nanopositioning system and the AFM tip was used to create a nano-scale Schottky contact in the vicinity of a QD. The photocurrent spectra clearly showed peaks from quantum dots located in the vicinity of the AFM tip. The spatial resolution of the method was determined to be in between 100 nm and 1000 nm. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this article, Au/titanylphthalocyanine/n-GaAs diodes incorporating ultrathin films of the archetypal organic semiconductor titanylphthalocyanine were investigated by ballistic electron emission microscopy/spectroscopy (BEEM/S). BEEM/S measurements were used to determine the transmission of ballistic electrons through titanylphthalocyanine as a function of energy and temperature. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this work, photocurrent images of lithographically processed GaAs/AlAs heterostructures are recorded by an atomic force microscope. It is found that the AFM tip sample contact is strongly dependent on the thickness of the native oxide layer on the sample surface. Therefore, the photocurrents increase if a successively increasing tip sample force is applied, which leads to a gradual penetration of the surface oxide layer. Due to the complex behavior of the photocurrent as a function of tip-bias and tip-force, the contrast in photocurrent images is non-monotonic and can be reversed under appropriate bias and force conditions.

In this article Au/titanylphthalocyanine/GaAs diodes incorporating ultra smooth thin films of the archetypal organic semiconductor titanylphthalocyanine (TiOPc) were investigated by Ballistic Electron Emission Microscopy/Spectroscopy (BEEM/S). Analyzing the BEEM spectra, we find that the TiOPc increases the BEEM threshold voltage compared to reference Au/GaAs diodes. From BEEM images taken we conclude that our molecular beam epitaxial (MBE) grown samples show very homogeneous transmission, compare to wet chemically manufactured organic films. The barrier height measured on the Au- TiOPc-GaAs is Vb ≈ 1.2eV, which is in good agreement with the data found in [T. Nishi, K. Tanai, Y. Cuchi, M. R. Willis, and K. Seki Chem. Phys. Lett., vol. 414, pp. 479-482, 2005.]. The results indicate that TiOPc functions as a p-type semiconductor, which is plausible since the measurements were carried out in air [K. Walzer, T. Toccoli, A. Pallaori, R. Verucchi, T. Fritz, K. Leo, A. Boschetti, and S. Iannotte Surf. Scie., vol. 573, pp. 346-358, 2004].

Photocurrent (PC) spectroscopy is employed to study the carrier escape from self-assembled InAs/GaAs quantum dots (QDs) embedded in a Schottky photodiode structure. As a function of the applied field, we detect a shift of the exciton ground-state transition due to the quantum-confined Stark effect ( S = 4.3 meV / V ). The tunneling time, which is directly related to the observed photocurrent linewidth due to τ ∼ ℏ / ( 2 Γ ) , changes by a factor of five in the photocurrent regime. The measured linewidth dependency on the electric field is modeled by a simple 1D WKB approximation for the tunneling process, which shows that the energetic position of the wetting layer is important for the measured tunneling time out of the dot. In addition to that we present cross-sectional atomic force measurements (AFM) of the investigated photodiode structure. The method needs a minimum of time and sample preparation (cleaving and etching) to obtain the dot density, dot distribution, and give an estimate of the dot dimensions. Etching only the cleaved surface of the sample opens up the opportunity to determine the properties of a buried dot layer before or even after device fabrication.

In this paper we describe how cross-sectional ballistic electron emission microscopy (XBEEM) can be used to measure the Schottky barrier height profile of a GaAs/AlGaAs multi heterostructure in cross-sectional geometry. By recording ballistic electron spectra across the heterostructure with a local resolution in the nm range, it is found that the measured Schottky barrier height profile is smeared out compared to the conduction band profile calculated from the sample growth parameters. We attribute this behavior to lateral band bending effects along the heterojunction. In addition, we have evidence that the barrier height profile is influenced by single impurities in the AlGaAs layers.

In this work, quantitative scanning capacitance spectroscopy studies on bulk GaAs samples and InAs quantum dots are carried out in an ambient atmosphere. The experimental results are described by a simple spherical capacitor model, and the corresponding barrier heights and sample dopings are determined. We further find a strong dependence of the C(V) data on the applied tip force. The barrier height decreases significantly with increasing pressure.

In this work, we present a carrier escape study from InAs/GaAs self assembled QD's by the use of photocurrent measurements. As a function of the applied field, we detect a shift of the exciton ground state transition due to the quantum-confined Stark shift. ?From the measured Stark shift S = 4:3 meV we deduce a exciton dipole moment of p = (4.3 ± 0.2) × 10–29 Cm. The tunneling time, which is directly related to the observed photocurrent linewidth due to τ ∼ ħ/(2Γ), changes by a factor of five in the photocurrent regime. The measured linewidth dependency on the electric field is modelled by a simple 1D WKB approximation for the tunneling process, which shows that the energetic position of the wetting layer is important for the measured tunneling time out of the dot. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Semiconductor heterostructures, such as double-barrier resonant tunnelling diodes and superlattices, are nowadays used for many applications. One very versatile and powerful method to study electronic transport in heterostructures is hot electron spectroscopy. Hot electron spectroscopy can be carried out in two complementary versions: device-based techniques usually employ so-called hot electron transistors (HETs), while ballistic electron emission microscopy (BEEM) uses a scanning tunnelling microscope (STM) as the source of ballistic electrons.In this review, spectroscopic results obtained by these two methods are compared and discussed. It is shown that BEEM results are strongly influenced by electron refraction effects, while the behaviour of HET devices is dominated by inelastic scattering effects in the base and drift region of the device. Thus, STM-based BEEM/S and HET-based spectroscopy are genuinely complementary methods, which yield supplementary results.

In this article we explore the application of scanning capacitance microscopy (SCM) for studying focused ion beam (FIB) induced damage in silicon. We qualitatively determine the technologically important beam shape by measuring the SCM image of FIB processed implantation spots and by comparison of topographical and SCM data. Further, we investigate the question how deep impinging ions generate measurable damage below the silicon surface. For this purpose, trenches were manufactured using FIB and analyzed by SCM in cross-sectional geometry.

We have investigated the impact of shrinking feature sizes on the sputter efficiency of focused ion beams on crystalline silicon. On the basis of this analysis, we have demonstrated the main competitive mechanisms determining the complex response of silicon. Low-dose irradiation with a 50-keV Ga+ beam in the range from 1013 ions/cm2 to 1015 ions/cm2 produced pronounced swelling of the silicon due to amorphization. Higher doses led to material removal with an efficiency of about 2.5 atoms/ion. A sputter yield promoting the self-focusing effect combined with the sputter rate increase at oblique angles, and an opposing dose-deficiency effect, determined the complex characteristics of nanoscale trench milling. Shrinking critical dimensions led to higher sputter yields, attributable to self-focusing effects of incident ions becoming dominant at aspect ratios in the region of unity. At aspect ratios beyond unity, re-deposition was the dominant effect.

In this paper we explore the application of scanning capacitance microscopy (SCM) for studying focussed ion beam (FIB) induced damage in silicon. We qualitatively determine the technologically important beam shape by measuring the SCM image of FIB processed implantation spots, and by comparison of topographical and SCM data. Further, we investigate how deep impinging ions generate measurable damage below the silicon surface. For this purpose, trenches were manufactured using FIB and analysed by SCM in cross-sectional geometry.