Nitrogen-related Defects Research Articles

Femtosecond laser interaction with pulsed-laser deposited carbon thin films of nanoscale thickness

The dependence of optical, electronic and thermal penetration zones on the thickness of nanoscale layers grown on silicon wafers is reported. Tetrahedral amorphous carbon (ta-C) and amorphous carbon nitride (a-CxNy) films were prepared by inverse pulsed laser deposition (IPLD). Single-pulse modification thresholds for femtosecond laser processing proved to be dependent on the actual film thickness below 60 nm for ta-C and 90 nm for a-CxNy. The modification behaviour was governed by multiphoton processes. An effective penetration depth of the laser radiation in a-CxNy was of ca. 110 nm in accordance with two-photon absorption. Both the emergence length of ballistic hot electrons and the heat diffusion length are negligible in these thin film materials. The lower bulk value of the threshold fluence of the a-CxNy films as compared to ta-C is mainly controlled by optical contributions due to nitrogen-related defects.

A density functional theory study of the atomic structure, formation energy, and vibrational properties of nitrogen-vacancy-oxygen defects in silicon

The atomic structure, energy, stability, vibrational spectra, and infrared absorption intensities of major intrinsic nitrogen-related defects in nitrogen doped silicon crystals have been investigated using ab initio density functional theory and semi-empirical quantum mechanics methods. The defects that are of interest are nitrogen-vacancy-oxygen complexes which are believed to affect oxygen precipitation and void formation as well as nitrogen concentration measurement in nitrogen-doped silicon. Several chemical reactions involving nitrogen, Si vacancies and oxygen interstitial have been studied. After relaxation, the local vibrational modes of each complex are calculated within the harmonic oscillator approximation and the infrared absorption intensities are evaluated from the dipole moment derivatives. By cross correlating the stability and the infrared active lines of the defect, and taking into consideration the symmetry group of each complex, we were able to emphasize which nitrogen related complexes are likely to control the oxygen precipitation and voids formation and to assert a new calibration relationship for nitrogen concentration measurement in nitrogen doped Czochralski and float zone silicon wafers.

Nitrogen and Luminescent Nitrogen‐Vacancy Defects in Detonation Nanodiamond

An efficient method to investigate the microstructure and spatial distribution of nitrogen and nitrogen-vacancy (N-V) defects in detonation nanodiamond (DND) with primary particle sizes ranging from approximately 3 to 50 nm is presented. Detailed analysis reveals atomic nitrogen concentrations as high as 3 at% in 50% of diamond primary particles with sizes smaller than 6 nm. A non-uniform distribution of nitrogen within larger primary DND particles is also presented, indicating a preference for location within the defective central part or at twin boundaries. A photoluminescence (PL) spectrum with well-pronounced zero-phonon lines related to the N-V centers is demonstrated for the first time for electron-irradiated and annealed DND particles at continuous laser excitation. Combined Raman and PL analysis of DND crystallites dispersed on a Si substrate leads to the conclusion that the observed N-V luminescence originates from primary particles with sizes exceeding 30 nm. These findings demonstrate that by manipulation of the size/nitrogen content in DND there are prospects for mass production of nanodiamond photoemitters based on bright and stable luminescence from nitrogen-related defects.

Cathodoluminescence characterization of a nitrogen-doped homoepitaxial diamond thin film

Strong modification of the optical spectra is apparent in nitrogen-doped chemical vapor deposited (CVD) diamonds. Nitrogen-vacancy (NV) defects in CVD diamond are effectively created by nitrogen doping with a high concentration of the gaseous phase. In particular, the 575 nm center and 637 nm centers are enhanced in intensity at a N doping level of around 1018 at./cm3, while nitrogen addition during CVD growth leads to quenching of both the exciton and H3 centers. The influence of nitrogen doping on the exciton and NV defect states in a homoepitaxial CVD diamond thin film was investigated by high-resolution cathodoluminescence experiment. In addition, Raman experiments were performed to detect the internal stress. The results show that the exciton and nitrogen-related defect emission spectra underwent a shift of the peak position to a longer wavelength by nitrogen doping. The characteristic Raman peak of diamond at 1332 cm−1 showed a shift toward lower wave numbers with increasing nitrogen incorporation.

Impact of nitridation on recoverable and permanent negative bias temperature instability degradation in high-k/metal-gate p-type metal oxide semiconductor field effect transistors

Negative bias temperature instability is investigated on TaN metal-gated HfSiO(N) p-type metal oxide semiconductor field effect transistors. A previously developed measurement technique that allows to distinguish between the recoverable and the permanent components of the Vth shift is employed. When applied to nitrided and nonnitrided stacks, it is found that the permanent component is at most weakly influenced by the nitridation, while the recoverable component is strongly enhanced in the nitrided stacks. The nitrogen-related defect, which is responsible of the recoverable component increase, is clearly observed in the stress induced leakage current spectrum.

Distinct Clockwise Capacitance−Voltage Hysteresis in Aminopropyl-silsesquioxane Thin Films

Aminopropyl-silsesquioxane resins and thin films were synthesized from aminopropyltrimethoxysilane (APTMS). To investigate the changes in the molecular structure of the film with increasing curing temperature, Fourier transform infrared spectroscopy (FT-IR) was performed. The dielectric properties of the thin films were investigated by capacitance−voltage (C−V) measurements in a metal−insulator−semiconductor (MIS) structure. To explain the spectral changes in the FT-IR results, it is proposed that the Si−OH and aminopropyl groups freely exist without hydrogen bonding interactions in the curing temperature range 100−200 °C, while molecular structures such as N(Si≡)3, N(Si≡)2, and O(Si≡)2 are formed at higher temperatures in the range 250−300 °C. The dielectric constant values and dissipation factors are regarded as being suitable for electronic applications, e.g., the gate insulators of organic thin film transistor (OTFT) devices. Interestingly, amphoteric charge trap behavior, such as a distinct clockwise C−V hysteresis, was observed in the sample cured at 300 °C. It is proposed that this originates from the coexistence of N(Si≡)2 and E′ centers in the cured films, into which positive charges or negative charges originating from the metal gate electrode are trapped, depending on the polarity of the applied electric field. It seems that the nitrogen-related molecular defects act as electron trap centers in the aminopropyl-silsesquioxane thin films.

Chemical controllability of charge states of nitrogen-related defects inHfOxNy: First-principles calculations

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Optical properties of zinc nitride thin films fabricated by rf-sputtering from ZnN target

RF-magnetron sputtering was employed to deposit zinc nitride films, from zinc nitride target, in plasma containing a mixture of Ar–N 2 gases. The effect of ambient atmosphere as well as thermal treatments (annealing in nitrogen and oxidation) on the optical properties of the films were examined. The transparency and conductivity of the films just after deposition were dependent on the amount of Zn in the structure. The films exhibited n-type conductivity and wide optical band gap. Annealing improved their transparency but they became more resistive. Oxygen was detected in films remained in the ambient atmosphere for a long period of time just after deposition, affecting transmissivity. Annealing promoted adsorption of oxygen in their structure, and the optical properties of high temperature annealed films resembled those of zinc oxide films having nitrogen as acceptor dopant. Band-edge emission peaks arising from acceptor exciton as well as nitrogen-related defect centers were revealed by low temperature photoluminescence.

1.55 μ m GaAs∕GaNAsSb∕GaAs optical waveguides grown by radio frequency nitrogen plasma-assisted molecular beam epitaxy

We demonstrate a 1.55μm GaAs∕GaNAsSb∕GaAs optical waveguide grown by molecular beam epitaxy as an alternative to the AlGaAs∕GaAs system. The 0.4-μm-thick GaNAsSb guiding layer contains ∼3.5% of N and 9% of Sb, resulting in optical band gap of 0.88eV. The refractive index of the GaNAsSb layer was measured from 800to1700nm. The GaNAsSb layer has a refractive index value of 3.42 at 1.55μm wavelength. The propagation loss measured using the Fabry–Pérot resonance method was found to be affected by nitrogen-related defect absorption.

Optical evaluation of carrier lifetime and diffusion length in synthetic diamonds

The key electronic parameters of high-pressure-high-temperature and chemical-vapor-deposition grown diamonds have been determined at interband ( hν = 5.82 eV) or below bandgap ( hν = 4.68 eV) photoexcitation, using a picosecond transient grating (TG) technique. TG kinetics directly provided the values of ambipolar diffusion coefficient (6–10 cm 2/s) and carrier lifetime (in a range from 0.17 to 2.8 ns) for crystals grown under different conditions. The carrier diffusion length was found to vary from 0.5 μm in CVD layers to 1.6 μm for IIa type HPHT diamond crystal. The carrier lifetimes correlated well with the nitrogen-related defect density in both types of diamonds.

Hall mobility and electron trap density in GaAsN grown by liquid phase epitaxy

The Hall mobility of GaAsN layers grown by liquid phase epitaxy (LPE) is studied as a function of the nitrogen content in the material. It is observed that the parameter decreases with increasing nitrogen in the layer, in agreement with earlier theoretical predictions assuming scattering of electrons in nitrogen-related defects. It is also found that the decrease in mobility is accompanied by a corresponding increase in the density of electron traps, believed to originate from different configurations of nitrogen defect centers. The observation clearly suggests that nitrogen-related defects are responsible for lowering the mobility in LPE-grown GaAsN.

Theoretical Aspects on the Formation of the Tri-Interstitial Nitrogen Defect in Silicon

In this paper we investigate the formation of interstitial nitrogen trimers N3 which have been suggested as a fast-diffusing species in silicon recently. Out-diffusion profiles of nitro- gen show the involvement of at least two independent nitrogen related defects in the diffusion process depending on the nitrogen concentration at different depths of the sample. When the nitrogen concentration is small it is proposed that nitrogen trimers are formed in a two step process. We present the structural properties of such a defect using density functional theory and examine the energetics of the two proposed reactions leading to the formation of N3.

Nitrogen-related point defect in 4H and 6H SiC

A nitrogen-related pair defect is studied as a function of doping density in 4H and 6H SiC. Electron paramagnetic resonance measurements verify that one nucleus in the pair is nitrogen, but the second part of the pair remains uncertain. The pair concentration varies monotonically with nitrogen concentration in samples with doping density 10 18–10 16 cm −3 and the boron concentration is an order of magnitude less than that of nitrogen. The pair center is not observed in the dark or under ultraviolet illumination when the nitrogen and boron concentrations are similar. We conclude that the pair is generated in all nitrogen-doped samples, but like the isolated nitrogen impurity, may be compensated by boron.

Recombination activity of nickel in nitrogen-doped Czochralski silicon treated by rapid thermal processing

The recombination activities of nickel (Ni) in p-type nitrogen-doped Czochralski (NCZ) silicon (Si) subjected to the rapid thermal processing (RTP) under different temperatures, atmospheres or cooling rates were investigated by means of microwave photoconductivity decay and scanning infrared microscopy. It was found that the value of the reciprocal of effective minority carrier lifetime (1/ τ eff) of NCZ Si, related to the recombination activity of Ni, increased with the annealing temperature or cooling rate, while, it was almost insensitive of the annealing atmosphere. Moreover, the 1/ τ eff of the Ni-contaminated NCZ Si was lower than that of the Ni-contaminated conventional Czochralski (CZ) Si annealed under the same condition. It is considered that the nitrogen-related defects or large grown-in oxygen precipitates might be the reason of relative lower recombination activity of Ni in NCZ Si.

Interaction of electron irradiation with nitrogen-related deep levels in InGaAsN

The authors present an investigation of 1MeV electron irradiation-induced defects in p-InGaAsN and their impact on nitrogen-related defects. A hitherto existing nitrogen-related electron trap E1 (0.20eV) shows a significant increase in concentration after 1MeV electron irradiation. In addition, 1MeV electron irradiation induced a hole trap H1 at energy of about 0.75eV above the valence band. Isothermal annealing analysis indicates that E1 is a complex defect involving an interstitial or a substitutional atom in combination with some other defect, whose concentration is enhanced by irradiation. A correlation exists between the recovery of free carrier concentration and recovery of the E1 center to preradiation concentrations, which indicates the possibility of the E1 as an acceptorlike center.

Postdeposition-Anneal Effect on Negative Bias Temperature Instability in HfSiON Gate Stacks

The effect of postdeposition anneals in various ambients on negative bias temperature instability (NBTI) in metal-organic chemical-vapor-deposited HfSiO(N) stacks is investigated. The nitrided stacks, either by anneal or decoupled plasma nitridation (DPN) followed by a postnitridation anneal in O2 or N2 (DPN + O2 and DPN + N2 ), are more degraded by NBTI than the nonnitrided ones (O2, N2 anneal, and as deposited stacks). Moreover, none of the nitrided stacks reaches the 10-year NBTI lifetime, while the lifetime for the nonnitrided ones is larger than 10 years. Nitrogen profiles measured by X-ray photoelectrons spectroscopy and charge-pumping-current data show a relation between nitrogen location and positively charged defects in the gate stack. The additional NBT degradation in nitrided stacks is due to filling or generation of nitrogen-related defects by holes that are injected from the channel.

Improvement of GaInNAs p-i-n photodetector responsivity by antimony incorporation

Deep-level transient spectra (DLTS) and photoresponsivity were measured for Ga0.90In0.10N0.033As0.967∕GaAs and Ga0.96In0.04N0.028As0.967Sb0.005∕GaAs p-i-n photodetector structures. The GaInNAs and GaInNAsSb layers were grown closely lattice matched to GaAs substrate at 460°C using molecular beam epitaxy. Two hole-trap levels were observed in the DLTS spectra of the GaInNAs sample with activation energies of 0.152 and 0.400eV (labeled as H-1 and H-2 peak, respectively). The lower activation energy is believed to be associated with nitrogen-related defects and the higher activation energy is associated with arsenic antisite defects (AsGa). Following the incorporation of Sb into GaInNAs, the H-1 peak vanished from the DLTS spectra of the GaInNAsSb sample, and the AsGa defect-related DLTS signal was significantly reduced. Analysis of the DLTS data also showed that the trap concentration related to AsGa was reduced from 2.15×1015to2.58×1014cm−3. The DLTS results are in good agreement with the photoresponsivity results, in which the GaInNAsSb sample showed 10× higher photoresponse compared to the GaInNAs sample. This indicates the incorporation of Sb into GaInNAs has effectively improved the p-i-n photodetector device performance.

On the interaction of molecular hydrogen with diamonds: An experimental study using nuclear probes and thermal desorption

Hydrogen behavior in monocrystalline diamonds with different concentrations and types of nitrogen defects was studied using Nuclear Reaction and micro-Elastic Recoil Detection Analyses and Thermal Desorption Spectroscopy. Diamonds were studied in as-received state, after HPHT treatment and after hydrogenation in molecular hydrogen. A considerable amount of hydrogen was found to be bonded to diamond surfaces. Kinetics of surface hydrogen desorption is similar to what was reported for plasma-hydrogenated diamonds. The solubility of hydrogen in type IIa diamonds is very low. The efficiency of hydrogen traps in diamond bulk varies with the dominant type of nitrogen-related defects. The cross-section of traps decreases in row Ib > IaA > IaB diamonds, though binding energy in type IaB crystals may be higher, than in type IaA. Dislocations may promote hydrogen diffusion. A marked dependency of the hydrogen content and diffusivity between diamond growth sectors were observed for some samples. The total hydrogen content is higher in octahedral sectors.

Raman analysis of nitrogen doped ZnO

The mechanism of nitrogen doping is essential for making p-type ZnO. This paper demonstrates that Raman characterization is a potentially powerful tool to study the mechanism of nitrogen doping. We have observed new Raman features near 280, 510, 570, 642, 773, 1360 and 1565 cm − 1 shift in nitrogen doped ZnO (ZnO:N) thin films compared with undoped ZnO films. Peaks at 280, 510, 570, 642, and 773 cm − 1 are attributed to the nitrogen related defect complex. The Raman peaks at 1360 cm − 1 and 1565 cm − 1 shift are assigned to D—(disordered) and G—(Graphitic) bands associated with the carbon-related defect complex, respectively. The intensity and the intensity ratio of peaks at 1360 cm − 1 and 1565 cm − 1 have been found to be sensitive parameters that reflect the conductivity type of ZnO:N. Explanations are presented which correlate the Raman features to the electric conductivity of the films. From this analysis, we found that at temperature lower than or at 400 °C, nitrogen incorporation will form the nitrogen or possible nitrogen carbon related defect complex. As the growth temperature increases to 500 °C, the features associated with nitrogen are difficult to distinguish and the features associated to carbon begin to emerge. This observation possibly indicates the decrease of the nitrogen content and the increase of the carbon content in the ZnO:N film. The increase of carbon content may affect the donor behavior of the film. This observation suggests that growth conditions should be controlled to avoid carbon into the film.

Negative bias temperature instabilities in HfSiO(N)-based MOSFETs: Electrical characterization and modeling

Negative bias temperature instabilities (NBTI) in SiO x (N)/HfSiO(N)/TaN based pMOSFETs are investigated. It is shown that nitrogen-incorporation in the gate stack (either by NH 3 anneals or decoupled plasma nitridation, DPN) result in much enhanced NBTI. Device degradation is mainly due to fast (interface) state generation in the non-nitrided stacks, while a substantial contribution of the defects produced in the nitrided stacks are slow (bulk) states. The kinetics of fast interface states is modeled within a reaction-dispersive transport model, taking into account the dispersive transport of protons generated from the depassivation of trivalent Si dangling bonds at the Si/SiO x interace ( P b0 centers). The generation of slow states in the nitrided stacks is simulated by an electrochemical model, considering the electric field and hole assisted breaking of nitrogen-related defects, tentatively attributed to Si 2N or Hf 2N dangling bonds. A correlation between NBTI and recovery is also found, namely that enhanced NBTI in nitrided stacks results in enhanced recovery. This suggests that recovery mainly arises from the detrapping of holes at the N-related defects.