SiC is a material that seems ideal for high-power, high frequency and high temperature electronic devices. It does not suffer from large reverse recovery inefficiencies typical for silicon when switching. In contrast to silicon, SiC is however difficult to dope by diffusion, and instead ion-implantation is used to achieve selective area doping. The drawback of this technique is that irradiating the crystal with dopant atoms creates a great deal of lattice damage including vacancies, interstitials, antisites and impurity-radiation defect complexes. Although many of the point defects can be eliminated through thermal annealing, some however, e.g. the photoluminescence (PL) DI and DLTS Z1/Z2 centers in ·4H-SiC, are stable to high temperatures. In this polytype, DI and the related alphabet lines are the most prominent PL signals. The latter can be seen directly after low energy irradiation while DI usually dominates the PL spectrum of implanted and irradiated SiC after annealing. Not only implantation but also rapid growth of SiC by CVD methods leads to a deterioration in quality with an increase in electrically active grown in defects. Among these, the Z1/Z2 defects are dominant in n-type 4H-SiC, as well as material that has been exposed to radiation. We use first principles density functional calculations to investigate defect models for the above mentioned defects in 4H-SiC and relate their electrical and optical activity to experiments.

The dilute GaNxAs1-x alloys (with x up to 0.05) have exhibited many unusual properties as compared to the conventional binary and ternary semiconductor alloys. We report on a new effect in the GaNxAs1-x alloy system in which electrically active substitutional group IV donors and isoelectronic N atoms passivate each other's activity. This mutual passivation occurs in dilute GaNxAs1-x doped with group IV donors through the formation of nearest neighbor IVGa- NAs pairs when the samples are annealed under conditions such that the diffusion length of the donors is greater than or equal to the average distance between donor and N atoms. The passivation of the shallow donors and the NAs atoms is manifested in a drastic reduction in the free electron concentration and, simultaneously, an increase in the fundamental bandgap. This mutual passivation effect is demonstrated in both Si and Ge doped GaNxAs1-x alloys. Analytical calculations of the passivation process based on Ga vacancy mediated diffusion show good agreement with the experimental results.

Pendeo-epitaxy has been applied to nonpolar a-plane GaN layers in order to observe if such process will lead to defect reduction in comparison with direct growth on this plane. Uncoalesced and coalesced a-plane GaN layers with thicknesses 2μm and 12μm, respectively, have been studied by conventional and high resolution electron microscopy. The following structural defects have been observed in pendeo-epitaxial layers: (1) basal stacking faults, (2) threading dislocations, and (3) prismatic stacking faults. A drastic decrease in the density of threading dislocations and stacking faults was observed in ‘wing’ areas with respect to ‘seed’ areas. Cross-section images reveal cracks and voids at the areas where two coalesced wings meet each other. High resolution electron microscopy shows that the majority of stacking faults are low-energy planar defects of the types I1, I2 and I3. The I3 type basal stacking fault, predicted theoretically, was observed experimentally for the first time.

ZnO films with orientations of (001), (110), and (100) were fabricated on silicon by different substrate biases at low temperature. Dynamic cathodoluminescence (CL) dependence on electron bombardment revealed unstable Zn-N bonding if N2 was used as a predecessor. CL under various accelerated voltages showed the possible energies of Zn-N. N-related photoluminescence (PL) at low temperature confirmed that nitrogen was released after annealing. These N-doping behaviors agreed to the theoretical calculation.

The co-implantation of germanium, carbon, and boron with the optimum implant energies and doses makes it possible to create p+/n junctions with the sheet resistance of less than 600 Ohm/square and the slope of less than 3 nm/decade. The narrow process window is based on careful engineering of the amorphization, point defects, and stresses and includes standard 1050°C spike annealing. The germanium pre-amorphization suppresses the ion channeling for the subsequent boron implant. The tensile stress induced by the substitutional carbon atoms and the compressive stress induced by the substitutional germanium atoms slow down boron diffusion and help to make the junctions shallower. The stress gradient in the transition region from the strained carbon and germanium doped layers to the relaxed silicon underneath creates an uphill boron flux that makes the junction slope steeper.

The optimum amount of carbon is placed in between the implanted boron and the implant damage, which is located below the amorphized layer. During the annealing, the carbon atoms capture silicon interstitials that are coming from the implant damage and form carbon-interstitial clusters. The analysis demonstrates that it is possible to capture over 95% of the interstitials this way before they have a chance to reach boron-doped layer. This completely suppresses the transient-enhanced boron diffusion (TED) and drastically reduces the amount of boron that is deactivated in boron-interstitial clusters (BICs). In fact, the point defect engineering with an optimized carbon profile allows to remove all non-equilibrium silicon interstitials that are generated by the following three sources: the implant damage below the amorphized layer, the rapid temperature ramp down, and the interstitials generated by boron at high concentrations (due to the effect known as boron-enhanced diffusion (BED)).

The latter effect leads to significant increase of the apparent boron activation level beyond the well-characterized solid-state solubility level. We explain this effect as a reduction in formation of BICs due to the lack of interstitial supersaturation. In carbon-free silicon, high concentration boron is always accompanied by the non-equilibrium interstitials, coming from either the implant damage or the BICs even if boron is introduced into silicon by pre-deposition instead of the implantation. Extensive experiments and theoretical analysis based on simulation of the interaction of Ge, C, I, and B atoms, as well as the stress effects, point to the optimized process flow that improves the shape and parameters of the p+/n USJs.

Low temperature pulsed electrically detected magnetic resonance (pEDMR) measurements of charge trapping and recombination transitions involving Pb centers at the c-Si (111)/SiO2 interface are presented. The results of these experiments show that when a conduction electron is trapped, it forms a strongly coupled spin pair with the defect electron prior to its readjustment into the charged Pb ground state. The data reveals that the Landé factors of the two electrons within these pairs are almost identical (difference < 0.002) and that they are, within the measurement accuracy, identical to the Landé factor of the uncharged, singly occupied Pb center. From this, it is concluded that trapping and recombination at Pb defects is dominated by direct charge capture and not by tunneling or hopping transitions from other localized states. Different cross sections attributed in previous studies to different interface defects at the c-Si/SiO2 interface can be explained by readjustment out of different spin configurations of the charged Pb-* defect.

Ge nanocrystals (NCs) of diameter 4–13 nm are grown embedded in a thermally grown SiO2 layer by Ge ion implantation and subsequent annealing. Steady state and time-resolved photoluminescence (PL) studies are performed on these embedded Ge nanocrystals to understand the origin of the PL emission at room temperature. Steady state PL spectra show a broad peak consisting of a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the Ge/SiO2 interface. Time-resolved PL studies reveal double exponential decay dynamics of the PL emission on the nanoseconds time scale. The faster component of the decay with large amplitude and having a time constant τ1∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ2∼10 ns is attributed to radiative recombination at the Ge NCs. These results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs.

The single-electron device (SED), which has quantum dot(s), or island(s) in its core, enables the control of electron motion on the level of an elementary charge. The single-electron pump and turnstile are members of the SED family and enable single-electron transfer synchronized with the gate clock. They have the potential for extremely low error rates of electron transfer and are thus expected to be building-block devices for future information processing and electrical metrology. We have been pursuing the fabrication of Si-based SEDs using CMOS technology with the help of electron-beam lithography and have recently demonstrated a Si single-electron pump and turnstile. They are composed of one Si quantum dot and two tiny MOS gates and have dramatically increased the operation temperatures, which opens up the possibility of the practical use of the pump and turnstile.

Another path to realizing single-electron transfer, which we will discuss here, might be to use a localized state in the Si bandgap instead of quantum dots. The localized states could in principle be donor/acceptor levels or any other states created by crystalline imperfections. They are free from the problem of the critical size control of the quantum dots, which might lead to a new era of single-electronics in combination with the rapidly developing research field of “dopant engineering”.

The electrical performance of junctions in SiGe Strain Relaxed Buffers (SRB's) with a strained Si top layer is investigated. Most of the SRB's grown in this experiment use a thin C-doped SiGe layer, which allows to fabricate thin (∼250nm) SRB's with a high relaxation degree. The effects of Threading Dislocation Density (TDD) and C-rich layer depth on the electrical behaviour of n+/p and p+/n junctions are studied. The C atoms in the junction's Space Charge Region (SCR) give rise to defects and induce a noticeable increase in the leakage. The effect of the TDD on the leakage in n+/p junctions is linear over the complete voltage range applied, while for p+/n junctions, only a small effect on leakage is measured at V=1V reverse for TDD's below 1×107cm-2. For low reverse voltages, the current varies more linearly with TDD.

Polysilicon memory switching is demonstrated in vertical n-i-p diodes with TiN contacts and feature size 150 nm. An increase of more than three orders of magnitude forward current at +2 V is achieved after the application of a +8 V programming pulse. The programming pulse electro thermally melts the polysilicon through Joule heating, and the quenched diodes have higher forward current. By changing one of the contacts from TiN to TiSi2, polysilicon memory switching is eliminated, with high forward current in the diode before and after a programming pulse. The TiSi2 contact seeds the crystallization of polysilicon with fewer defects during fabrication, compared to crystallization with TiN-only contacts, as shown by transmission electron microscopy. The mechanisms for increased forward current induced by either programming the TiN-only contacted diodes or making one contact TiSi2 are discussed.

The formation of ion induced nanoscale patterns such as ripple, dots or pores can be described by a linear continuum equation consisting of a surface roughening term due to curvature-dependent sputtering or asymmetric attachment of vacancies, and a surface smoothing term due to thermal or ion-induced diffusion. By studying ion-induced dimple volume change using atomic force microscopy, we show a method to measure the ion-roughening coefficient. Using this method, we found the roughening coefficient í was 45 nm2/sec at 730K for initial ion etchings with 300 eV Argon ions. Cathodoluminescence measurements indicated Ga-vacancy formation during ion bombardment. The activation energy for surface relaxation after ion etching was about 0.12 eV as measured by reflection high energy electron diffraction.

The relation between electrically active defects in organic and polymeric semiconductor materials and degradation of devices such as loss of luminance is currently not understood. In this paper, we study defect related charge processes using electrical transients in polymeric and organic diodes. We monitor slow charging and discharging currents as a function of time for both virgin and electrically aged devices. The current transients are analyzed spectroscopically in time domain using a technique called Time Analyzed Transient Spectroscopy, which is similar to DLTS in its implementation. We observe highly stretched exponentials over 3—4 orders of magnitude in time up to thousands of seconds indicating existence of large distribution in time constants in aged PLED devices. We demonstrate ability to distinguish between different mechanisms of charge storage related to defect related processes in typical OLED and PLED.

Semiconductor nanoparticles have a range of potential applications in electronic, optoelectronic and spintronic devices. Zinc oxide (ZnO), a wide-bandgap semiconductor, has emerged as an important material for such applications. In this work, impurities in ZnO nanoparticles were investigated with infrared (IR) spectroscopy, and the results show the presence of CO2 impurities in ZnO nanoparticles. Isotopic substitution was used to verify the frequency assignment and the results demonstrate conclusively that the impurities originate from the precursors. Isochronal annealing experiments were performed to study the formation and stability of the CO2 molecules. In addition to unintentional CO2 impurities, we intentionally introduced hydrogen into ZnO nanoparticles. Our results show that post-growth annealing in hydrogen dramatically changes IR transmission, reflection and electrical properties of the nanoparticles.

Behavior of point defects in annealing is investigated a lot in order to suppress the Transient Enhanced Diffusion (TED) of boron as is urged by the development of integrated circuits. Surface annihilation possibility for point defects is very important in determining junction depth in the case of ultra-shallow doping. However the understanding on it is still ambiguous considering the inconsistent results on surface annihilation behavior. In this paper the variation of surface annihilation possibility is studied. The simulation on boron diffusion as well as silicon diffusion is performed. The evolution of Si clusters is simulated. By explaining experimental results with Kinetic Monte Carlo method based simulation, we proposed that surface annihilation possibility varies in different cases.

We introduce proton-proton scattering at a microprobe of 17 MeV protons to quantitatively image three dimensional hydrogen distributions in polycrystalline diamond at a lateral resolution better than 1 μm and high sensitivity. The images show that most of the hydrogen of a <110>-textured undoped polycrystalline diamond film is located at grain boundaries. The average amount of hydrogen is (8.1±1.5)·1014 atoms/cm2 along the grain boundaries which corresponds to about a third of a monolayer. The content within the grain is below the detection limit of 1.4·1016 atoms/cm2 (0.08 at-ppm).

In the present study, we have analyzed the influence of the silicon nitride (SiN) passivation layer properties on the mean dark current and the quantum efficiency of CMOS APS (Active Pixel Sensor) through electrical characterization of lot wafers processed with three different SiN passivation films. The SiN layers were characterized by Spectroscopic Ellipsometry (SE) and Fourier Transform Infra Red (FTIR) spectroscopy to get the optical indices and the hydrogen content of the films, respectively. Hydrogen desorption was also studied by Thermal Desorption Spectrometry (TDS) experiments.

The different chemical bond concentrations enable to explain the device performance. It is shown that high [Si-H] and low [Si-N] bonds concentrations lead to high hydrogen desorption from the SiN films. Thus, the lowest dark current values have also been obtained with such silicon nitride passivation layers. Consequently, results are in agreement with the hydrogen passivation of defects being responsible of thermally generated carriers. Concerning the quantum efficiency (QE), it is highly influenced by the optical indices of the SiN passivation layer.

Actually, the thickness and complex refractive index of the SiN layer affect the light reflection, while the light absorption, in the visible range, is controlled by the [Si-Si] bonds concentration. There are also competing requirements to minimize dark current and to maximize quantum efficiency. In fact, high [Si-H] and low [Si-N] bonds concentrations (for good passivation) are generally observed in silicon-rich SiN films, which also contain high amount of [Si-Si] bonds (inducing high absorption, thus low QE). Increasing simultaneously the [Si-H] and [N-H] bonds concentrations in the passivation layer can be a way to have high hydrogen desorption during passivation anneal just preserving a transparent layer.

Recently, germanium based semiconductor device technology gained renewed interest due to new developments such as the use of high-k dielectrics for high mobility Ge MOSFETS. However, a systematic local structural investigation of clustering of dopants has been lacking in the literature. In this study, we present a detailed local structural analysis of boron and phosphorus implanted Ge wafers. We have used Ge K-edge x-ray absorption fine-structure spectroscopy (XAFS) in order to probe the local structural modifications around the Ge atom under various implantation parameters and postimplantation annealing treatments. The (100) Ge wafers were implanted and with 11B+ or 31P+ using energies ranging from 20 keV to 320 keV and doses of 5×1013 to 5×1016/cm2. Pieces of the implanted wafers were subjected to thermal annealing at 400°C or 600°C for three hours in high purity nitrogen. Secondary ion mass spectrometry (SIMS) measurements on these wafers were used to correlate the dopant concentration profiles with the local structural information obtained from XAFS. B and P implanted Ge exhibit distinct responses to annealing. For the P implanted Ge samples annealing leads to recrystallization of Ge with increasing annealing temperature, but also an increase in Ge Debye-Waller factors, whereas B implanted Ge samples e×hibit recrystallization at 400°C annealing but more randomness after 600°C annealing.

Heterojunction band offsets of GaNAsSb/GaAs, GaInNAsSb/GaAs, and GaInNAsSb/GaNAs/GaAs quantum well (QW) structures were measured by photoreflectance (PR) spectroscopy. These samples were grown by solid-source molecular beam epitaxy using a radio-frequency nitrogen plasma source. PR spectra were collected from the QW structures and the energy transitions were obtained. The experimental data of the QW energy transitions were analyzed by theoretical calculations. Using predetermined values such as QW thickness and composition, unknown factors such as the heterojunction band offsets were able to be determined. For the GaN0.02As0.87Sb0.11/GaAs structure, we found that Qc≈0.5. For Ga0.62In0.38N0.026As0.954Sb0.02/GaAs, we found that Qc≈0.8. This value is similar to the antimony free dilute-nitride material GaInNAs since the small amount of antimony does not affect the band offsets. For the technologically important Ga0.61In0.39N0.023As0.957Sb0.02/GaN0.027As0.973/GaAs laser structure, we found that the GaInNAsSb/GaNAs QW had a conduction band offset of 144 meV and a valence band offset of 127 meV. With a greater understanding of the band structure, more advanced GaInNAsSb laser devices can be obtained.

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: tempertature, cooling rate, oxidation time, impurity content. The interaction between point defects with extended defects and impurities affect the Si-SiO2 interface properties. The influences of point defects may be diminished and the interface properties improved by an appropriate choice of oxidation conditions.

The defects caused by hydrogen ion (H+) implantation were studied for heavily arsenic (As), boron (B), and phosphorous (P) doped (100) silicon substrates. At the implantation energy of 170keV, H+ beam generates defect zones in both arsenic and boron doped silicon wafers. The width of implant damage zone in the heavily As-doped silicon increased from 138nm to 415nm when H+ ion implant dose increased from1×1016 ion//cm2 to 5×1016 ion/cm2, respectively. This dependence is however, opposite in the heavily B-doped substrate. The defect zone decreased with increasing H+ ion dose. The second ion mass spectrometry (SIMS) data show that in both heavily As- and P-doped silicon substrates, hydrogen distribution was governed by both H+-dopant pairing reaction and the amount of the crystal damage, whereas it is exclusively determined by pairing reaction in heavily B-doped silicon substrates. The atomic force microscope (AFM) measurement indicated that the rms roughness of the as-exfoliated surface was 18.86nm, 13.06nm, and 6.79nm for P-, As- and B-doped silicon substrates, respectively. An rms roughness improvement of 20nm-170nm was observed when wafers were annealed at 270°C.