Hydrogen-related Defects Research Articles

Isoelectronic hydrogen-related defects in silicon

We report data for two hydrogen-related radiation-damage centres, known as the and centres, and compare their properties with the other `B' centres in silicon. We show that the radiative lifetimes of the luminescence are long, for the centre at 6.5 K and for the centre at 2 K, consistent with the luminescence occurring from excitons bound to centres which are isoelectronic with the silicon lattice. The energies of the bound-exciton multiplet states and their response to magnetic fields can be fitted precisely when the primary axis of each centre is close to a axis in the silicon. The excitons have spectroscopic binding energies of 12 and 18 meV for the two centres. However, the vibronic sidebands indicate that relaxations of meV occur when the excitons are bound. The centres are thus excellent examples of defects whose excited states are resonant with the crystal band states until stabilized by the relaxation. Comparison of the properties of the known shallow hydrogen-related radiation-damage centres in silicon shows that they form a unified class of similar defects.

Hydrogen-related defects in polycrystalline CVD diamond.

Hydrogen-related defects in polycrystalline CVD diamond.

Enhanced hydrogenation in polycrystalline silicon thin films using low-temperature ultrasound treatment

Ultrasound treatment (UST) was applied to improve electronic properties of polycrystalline silicon films on silica-based substrates. A strong decrease of sheet resistance by a factor of two orders of magnitude was observed in hydrogenated films at UST temperatures lower than 100 °C. This is accompanied by improvement of a film homogeneity as confirmed by spatially resolved photoluminescence study. The UST effect on sheet resistance demonstrates both stable and metastable behavior. A stable UST effect can be accomplished using consecutive cycles of UST and relaxation. An enhanced passivation of grain boundary defects after UST is directly measured by nanoscale contact potential difference with atomic force microscope. Two specific UST processes based on interaction between the ultrasound and atomic hydrogen are suggested: enhanced passivation of grain boundary defects and UST induced metastability of hydrogen related defects.

Theoretical Study of Hydrogen in Cubic Gan

AbstractPreliminary results of theoretical studies of hydrogen and hydrogen-related defects in cubic GaN are reported. Our calculations contrast with those of other authors in that the host crystal is represented by molecular clusters rather than periodic supercells, and that they are obtained using an all-electron methodology rather than the single effectiveparticle approach of density-functional theory. Our results confirm some predictions of other authors but conflict with others.

Hydrogen-related defects in Si

Hydrogen-related defects in Si

Relationship Between Hydrogen-Related Metastable Defect And EL2-Level In GaAs Crystals

AbstractThe relationship between the hydrogen-related metastable defect (M3/M4) and the EL2 level in n-GaAs crystals has been investigated. We found with various kinds of GaAs crystals that the hydrogen-related metastable couple (M3/M4), first reported by Buchwald et al., has been observed only in the crystals containing the EL2 defect. This fact was further confirmed by using LT-MBE GaAs crystals before and after rapid thermal annealing (RTA). Only in the n-LT-n sample annealed at 900°C, in which the EL2 defect was formed, the metastable couple (M3/M4) appeared upon hydrogenation. As hydrogenated, the EL2 level was passivated or dissociated. From bias-annealing experiments, the M4 level was completely annihilated by annealing at 573K, where the EL2 level was restored to its original concentration. We speculated from these results that both diffused hydrogen and preexisting arsenic antisite defect (AsGa) are responsible for the formation of the metastable defect(M3/M4).

Improvement of Poly-Silicon Thin Films and Thin Film Transistors Using Ultrasound Treatment

AbstractUltrasound treatment (UST) was applied to improve electronic properties of polycrystalline silicon films on silica-based substrates. A strong decrease of sheet resistance by a factor of two orders of magnitude was observed in hydrogenated films at UST temperatures lower than 100°C. This is accompanied by improvement of a film homogeneity as confirmed by spatially resolved photoluminescence study. The UST effect on sheet resistance demonstrates both stable and metastable behavior. A stable UST effect can be accomplished using consecutive cycles of UST and relaxation. An enhanced passivation of grain boundary defects after UST was directly measured by nano-scale contact potential difference with atomic force microscope. Two specific UST processes based on interaction between ultrasound and atomic hydrogen are suggested: enhanced passivation of grain boundary states and UST induced metastability of hydrogen related defects. We also demonstrate a utility of UST for improvement of leakage current and threshold voltage in hydrogenated poly-Si thin film transistors.

Characterization Of Hydrogen-Related Defects In Iron-Doped Indium Phosphide

AbstractWe have investigated the effect of annealing on hydrogen-related donors in crystals of InP using Hall effect, infrared absorption, and photorefractive gain measurements. Hydrogen is believed to be incorporated during growth, forming a donor complex around an indium vacancy with hydrogen saturating all four dangling bonds. By observing the local vibrational mode of the hydrogen complex using infrared absorption at 2316 cm−1 was possible to observe a decrease in the concentration of the hydrogen defect after annealing. In the undoped crystal, the disappearance of this defect is accompanied by a decrease in the free carrier concentration as measured by Hall effect. These changes are correlated with a decrease in the absorption due to Fe2+ centers, which form when donors are compensated by the neutral acceptor Fe3+. The existence of the hydrogen-related donor complex is further substantiated by photorefractive experiments using 1064nm irradiation on the iron doped samples. All of the measurements point to the role of hydrogen as a contributor to the net shallow donor concentration in InP crystals.

A Hydrogen-Related Defect in Polycrystalline CVD Diamond

A Hydrogen-Related Defect in Polycrystalline CVD Diamond

Metastability and Negative-U Properties for Hydrogen-Related Radiation-Induced Defect in Silicon

Metastability and Negative-U Properties for Hydrogen-Related Radiation-Induced Defect in Silicon

Hydrogen-related defects in crystalline semiconductors: a theorist's perspective

Hydrogen is a common impurity in all semiconductors. Although it is sometimes deliberately introduced, hydrogen often penetrates into the crystal during device processing. It interacts with broken or weak covalent bonds, such as those found at extended and localized defect centers. The main results of these covalent interactions are shifts of energy levels out of (or into) the gap and new optical activity (infrared absorption and Raman scattering). The shifts in energy levels lead to the passivation (or activation) of the electrical activity of various centers. Hydrogen can also interact with the perfect crystal and with itself, sometimes leading to the formation of extended structures known as platelets. Finally, H also acts as a catalyst, dramatically enhancing the diffusivity of interstitial oxygen in Si. The consequences of these interactions are substantial changes in the electrical and optical properties of the crystal, and in the lifetime of charge carriers. The thermal stability of the complexes containing hydrogen varies from room temperature up to several hundreds of degrees Celsius, and the diffusion of H is trap-limited up to rather high temperatures. Hydrogen normally exists in more than one configuration and charge state in semiconductors. A range of experimental and theoretical techniques have been used to investigate the rich properties of hydrogen in semiconductors, and several extensive reviews focusing mostly on the experimental side of these issues have been published in the past five years. The present review focuses mostly on the theoretical work performed in this field. However, the most recent experimental results are also discussed, and the current understanding of hydrogen interactions in semiconductors summarized.

Defect formation and evolution in TeO2-containing borosilicate glass films derived from a sol-gel process.

Defects in glasses, such as the paramagnetic E' (a singly charged oxygen vacancy), the hydrogen-related doublets with different splittings, and the NBOHC's (nonbridging oxygen hole centers), are generally induced by irradiating the glasses with highly energetic photons (particles) or laser beams. We find in the present work that the paramagnetic Te E' and hydrogen-related doublets with a splitting of 1.1, 7.4, and 11.9 mT can be produced by heating the sol-gel derived ${\mathrm{SiO}}_{2\mathrm{\ensuremath{-}}}$${\mathrm{B}}_{2}$${\mathrm{O}}_{3}$-${\mathrm{TeO}}_{2}$ glass films in a hydrogen atmosphere. Optical color centers were also induced at 3.6, 4.0, and 4.2 eV, depending on the heat treatment conditions during the reducing process. On heating the reduced films in air, the paramagnetic NBOHC's occurred together with two optical absorption bands at 2.2 and 5.5 eV. The hydrogen-related defects can be clearly divided, by their different responses to the microwave power, into two groups. One includes the 1.1- and 7.4-mT doublets, which were recognized to be a variant of the Te E' center, and the other consists of the 11.9-mT doublet, which was a different defect species from the Te E' center. The Te E', 1.1-, and 7.4-mT doublets were found to be bleached more easily than the 11.9-mT doublet at a high temperature in the hydrogen atmosphere. The observed optical absorption bands at 3.6, 4.0, and 4.2 eV were tentatively attributed to some neutral oxygen vacancies on tellurium atoms in the structure, while the optical bands at 2.2 and 5.5 eV were assigned to the NBOHC's.

Magnetic perturbations of excitons bound to an isoelectronic hydrogen-related defect in silicon.

Magnetic perturbations of excitons bound to an isoelectronic hydrogen-related defect in silicon.

Piezospectroscopy of the [formula omitted] and fano series of singly ionised Zn in Ge

The systematical low-temperature (4.2 K) photoluminescence (PL) study of the formation kinetics of optically active centers in H and He implanted CZ Si, annealed in the temperature range of 200–1000°C is presented. The samples were implanted with H (energy E=80 keV, dose D=1015/1016 cm−2) and He (E=150 keV, D=5×1014 cm−2) ions. It was found that the annealing of H or He implanted samples leads to the appearance and evolution of a number of zero-phonon lines as well as of broad bands. The origin of the observed lines and bands is discussed. It is assumed that the strong stresses around hydrogen-related structural defects (voids, bubbles) during the annealing at 500–700°C of H implanted Si lead to the formation of a specific optical center M′ (∼1.012 eV PL line).

Photoluminescence of excitons bound to the isoelectronic hydrogen-related defects B711 (1.1377 eV) in silicon.

Photoluminescence (PL) spectra of excitons bound to the isoelectronic defects ${\mathit{B}}_{71}^{1}$ (1.137 68 eV principal no-phonon line) created in phosphorus-doped silicon grown in a hydrogen atmosphere as a result of irradiation by thermal neutrons were investigated in magnetic fields up to 12 T and under uniaxial stress. The ${\mathit{C}}_{3\mathit{V}}$ symmetry of these defects was determined unambiguously from the dependences of the Zeeman splitting and the intensities of spectral components on magnetic-field orientation. The ground state of the bound exciton is split into a doublet with approximately 30 \ensuremath{\mu}eV energy separation. This splitting, which is not evident in the zero-field spectra because of the selection rules, results in the appearance of an additional spectral component in a magnetic field. Using group theoretical methods we constructed a Hamiltonian for excitons bound to the ${\mathit{B}}_{71}^{1}$ isoelectronic center, which takes into account electron-hole coupling and interaction with external perturbations. The phenomenological parameters of this Hamiltonian were determined from the optimal fit between theoretical and experimental dependences of the PL peak positions and their amplitudes on magnetic field and uniaxial stress. The proposed model of these bound excitons explains all of our experimental observations.

Study of hydrogenation on near-surface strained and unstrained quantum wells

We have studied the effects of hydrogenation on the luminescence efficiency of near-surface strained InGaAs/GaAs and unstrained GaAs/AlGaAs quantum wells (QWs). By using two different materials with an analogous structure, we have been able to clarify the effects of substrate temperature, ion dosage, strain profile in the material, and material quality on the local hydrogen concentration. This in turn modifies the behavior of hydrogen, the formation of hydrogen-related defects, and the variation of luminescence efficiency from the near-surface QW.

Spectroscopy of Hydrogen-Related Defects in III-V Semiconductors by Nuclear Techniques

Spectroscopy of Hydrogen-Related Defects in III-V Semiconductors by Nuclear Techniques

Effect of electrolyte exposure on silicon dioxide in electrolyte-oxide-semiconductor structures

The effect of hydration and ion penetration in silicon dioxide has been studied by fabricating metal-oxide-semiconductor capacitors on oxide exposed to acidic solutions with and without bias. Changes in oxide properties due to exposure have been probed using avalanche injection. Oxide charge build-up and interface state generation in the capacitors have been monitored. The measurements show that before avalanche injection the capacitance-voltage plots for the various electrolyte exposure conditions are similar. However, oxide integrity degradation is different for cathodic bias compared with anodic bias or no bias. This is due to penetration of protons or hydroxyl ions in the oxide, producing hydrogen-related defects that effect trapping and interface state generation.

Defect levels in silicon bombarded with light ions

Defect levels produced by H +, D + and He + ion bombardment of silicon with different phosphorus doping and oxygen content have been investigated using deep-level transient spectroscopy. After He + implantation only pure damage defect levels occur, whereas after H + and D + implantation additional hydrogen-related defects are observed. Defect profiles are generally much broader than theoretical distributions. For vacancy-related defect levels both the peak concentration and the halfwidth of the profiles depend only on the Fermi energy. The broadening which increases with decreasing doping level is explained by a model based on electric-field-enhanced diffusion of the vacancies out of the collision cascades. For the most prominent hydrogen-related defect, E c−0.30 eV, a mechanism for its formation has been deduced. This defect is tentatively identified as (H–V) pair.

Hydrogen interactions with delocalized spin centers in buried SiO2 thin films

Defect centers have been investigated in bonded and etchback silicon-on-insulator materials following irradiation using electron paramagnetic resonance (EPR). Three different EPR centers are created in the top 0.1 μm of the SiO2 dielectric by either x-ray irradiation or vacuum ultraviolet (VUV) illumination. Two of the defects are the classic E′ center (⋅Si≡O3) and the amorphous silicon center (⋅Si≡Si3). The third EPR active defect center is characterized by g=2.0025 with an effective line width of 1.1 G. Longer irradiation times transform this new center into a hydrogen-related defect as observed by its two hyperfine lines split by 23.1 G. It appears that this defect is positively charged when EPR active. Using conventional capacitance versus voltage techniques, it is also found that irradiation leads to the generation of positive charge in the dielectric. This charge is located near the bottom Si/SiO2 interface, opposite the interface at which the paramagnetic centers are located.