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The behaviour of hydrogen in crystalline semiconductors has attracted considerable interest during several decades. Due to its high diffusion rate and ability to react with a wide variety of lattice imperfections such as intrinsic point defects, impurities, interfaces and surfaces, hydrogen is an impurity of fundamental importance in semiconductor materials. It has been already evidenced in previous investigations that the most fundamental hydrogen-related defects in-group IV semiconductors are interstitial hydrogen atoms occupying the bond-centre site (BC) or the interstitial tetrahedral site (T). Using first-principles calculations Van de Walle predicted similar properties of isolated hydrogen in other II–VI and III–V semiconductors. Another interesting prediction shown in that work was the existence of a universal alignment for the hydrogen electronic (−/+) level. Until now there is no direct experimental information regarding the individual isolated hydrogen states in compound semiconductors and most reported properties have been inferred indirectly. In the present work in-situ conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques are used to analyse hydrogen-related levels after low-temperature proton implantation in different II–VI and III–V semiconductors including GaAs, ZnO and CdTe. From these experimental observations the donor level of isolated hydrogen is found to keep almost a constant value in the absolute energy scale taking into account different band-offsets calculated for the whole group of semiconductors.

The piezospectroscopic analysis of point defects allows to describe fixed defects embedded in a crystal environment of immobile atoms. This description works well when all atoms vibrate around fixed equilibrium positions and these vibrations are much faster than the time scale of the experiment while the equilibrium positions do not evolve within this time scale. For some defects this condition is not fulfilled at temperatures of the DLTS experiment, which somehow is reflected in a departure from what the theory predicts. On the other hand, systematic discrepancies between results of theoretical piezospectroscopic analysis and experiment can be a valuable source of information about a defect. We discuss how these re-orientation processes can be identified from the observed piezospectroscopic parameters for a number of defect complexes observed in silicon and germanium with the use of the high-resolution Laplace Deep Level Transient Spectroscopy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The first data evidencing the existence of the donor level of the interstitial hydrogen in GaAs are presented. The abundant formation of the ( 0 / + ) donor level after in situ low-temperature implantation of hydrogen into the depletion layer of GaAs Schottky diodes has been observed and the activation energy and annealing properties have been determined by Laplace DLTS. The activation energy for electron emission of this donor state is 0.14 eV. Above 100 K the hydrogen deep donor state is unstable, converting to a more stable form when there are electrons available for the capture process. A slightly perturbed form of the hydrogen donor in its neutral charge state can be recovered by illuminating the sample. This process releases twice as many electrons as the ionisation process of the hydrogen donor state itself. This fact, by analogy with the silicon case, evidences the negative-U behaviour of hydrogen in GaAs.

We present a comprehensive review of implementation and application of Laplace deep-leve1 transient spectroscopy (LDLTS). The various approaches that have been used previously for high-resolution DLTS are outlined and a detailed description is given of the preferred LDLTS method using Tikhonov regularization. The fundamental limitations are considered in relation to signal-to-noise ratios associated with the measurement and compared with what can be achieved in practice. The experimental requirements are discussed and state of the art performance quantified. The review then considers what has been achieved in terms of measurement and understanding of deep states in semiconductors through the use of LDLTS. Examples are given of the characterization of deep levels with very similar energies and emission rates and the extent to which LDLTS can be used to separate their properties. Within this context the factors causing inhomogeneous broadening of the carrier emission rate are considered. The higher resolution achievable with LDLTS enables the technique to be used in conjunction with uniaxial stress to lift the orientational degeneracy of deep states and so reveal the symmetry and in some cases the structural identification of defects. These issues are discussed at length and a range of defect states are considered as examples of what can be achieved in terms of the study of stress alignment and splitting. Finally the application of LDLTS to alloy systems is considered and ways shown in which the local environment of defects can be quantified.

The stress-induced electronic level splitting pattern can provide information regarding the symmetry of a defect complex. If the components of the piezospectroscopic tensor are known it is also possible to deduce information about the lattice relaxation in the vicinity of the defect. Based on a complete piezospectroscopic analysis of the vacancy–oxygen complex in silicon we confirm that this defect has an orthorhombic symmetry in the stable configuration while in the unstable configuration of the saddle point on the reconfiguration trajectory we demonstrate that it has trigonal symmetry. The piezospectroscopic description of static defects is, in some cases, inadequate to deal with some defect complexes when they are observed at relatively high temperatures. This is often the case for the high-resolution Laplace deep level transient spectroscopy (DLTS) measurements. At very low temperatures the vacancy–oxygen–hydrogen complex has monoclinic symmetry while at the temperatures used by us for Laplace DLTS measurements the observed symmetry is orthorhombic due to fast hydrogen jumps. A similar re-orientation (position averaging) process occurs for the divacancy in silicon. However, this is true only for the divacancy in the single negative charge state while the symmetry of the complex in the double negative state is stable trigonal. We discuss how these re-orientation processes can be identified from the observed piezospectroscopic parameters for both cases.

In this study the use of the high-resolution Laplace DLTS combined with uniaxial stress has allowed us to investigate in detail the structure and electrical properties of the platinum–hydrogen-related complex PtH 2 . We correlate the defect electronic level with the results of other spectroscopic studies performed with electron paramagnetic resonance and far-infrared absorption measurements. The observed stress-induced peak splitting pattern confirms the orthorhombic-IC 2v symmetry of the complex. The re-orientation process of the defect can be observed at temperatures higher than the room temperature for all bias conditions.

We have observed the donor (Ec-0.22 eV) and acceptor (Ec-0.16 eV) levels related to hydrogen-carbon complexes in silicon. The donor level is only detected at low temperatures after proton implantat ...

The migration of monatomic hydrogen in crystalline silicon is governed by three potential energy surfaces corresponding to the three possible charges states of hydrogen. The H0 and H+ surfaces have minima at the bond-centre site (BC) and give rise to a donor state, whereas the H− surface has minimum at the interstitial tetrahedral site (T) giving rise to an acceptor state. We review the current experimental status regarding these surfaces. The BC-donor and the T-site acceptor are found to exist in two closely related forms, which we explain by a distortion of the energy surfaces when hydrogen is trapped in the silicon lattice at the nearby interstitial oxygen. We show how this oxygen distortion acts as a catalyst for the conversion from H− at T sites to H+ at BC sites and retards the migration of H+ through BC sites.

In this study the technique of Laplace transform (high resolution) deep level transient spectroscopy combined with the uniaxial stress method has been used to study a symmetry and the defect reconfiguration kinetics (the stress induced alignment) of some forms of hydrogen-related centres. We have confirmed the trigonal symmetry of the defect related to the isolated bond centred hydrogen. When hydrogen decorates the vacancy-oxygen pair (the A centre) the apparent defect orthorhombic symmetry is not lowered as a result of a very high hydrogen jumping rate between two unsaturated broken bonds of the vacancy. We also show that the stress-induced defect alignment in some cases can be related to the same microscopic mechanism of the hydrogen motion as it is for the diffusion process. PACS numbers: 68.55.Ln, 71.55.Cn, 73.40.Lq

The technique of Laplace transform deep level transient spectroscopy has been used to study the acceptor levels of platinum and gold diffused into dilute (0–5% Ge) SiGe alloys. The high-resolution spectra obtained display a fine structure that we interpret as the effect of alloy splitting in terms of the relative number of silicon and germanium atoms in the immediate proximity of the transition metal. We show that Ge atoms in the first and in the second shell of atoms surrounding the impurity perturb the electronic properties of the well-known Au and Pt acceptor defects. For both defects the spectral distributions indicate an overpopulation of Ge-perturbed sites as compared to randomly occupied sites. This can be quantitatively interpreted in terms of an enthalpy difference of ∼60 meV between configurations with zero or one Ge in the first or second shell surrounding the impurity.

We identify the acceptor levels (−/0) of the VH and V 2 H defects in silicon from comparison of DLTS and EPR annealing data. The levels are very close to each other and close to the acceptor level of the PV defect (the E-center) as well. In order to separate them, we have applied the high-resolution technique of Laplace DLTS and compared the formation and annealing properties of defects generated by implantation of hydrogen or helium. We further applied Laplace DLTS in combination with uniaxial stress to study the acceptor level at E c − E t =0.31 eV previously assigned to a vacancy-hydrogen–oxygen defect. We find, in accordance with recent EPR measurements, that the defect displays orthorhombic-I symmetry and rule out that it contains two hydrogen atoms. The defect can be understood as a single hydrogen atom bound inside the A-center, the well-known VO defect of silicon, and we denote it VOH accordingly. The observed orthorhombic-I symmetry arises because the hydrogen atom (at T =160 K) swiftly jumps among two equivalent sites across the (1 1 0) plane that contains the Si–O–Si bond. Previous studies have shown that hydrogenation of oxygen-rich electron-irradiated samples leads to the formation of VOH with simultaneous depletion of the A-center. Our structural data are in accordance with this dynamic behavior.

In situ deep level transient spectroscopy (DLTS) has been applied to investigate n-type silicon implanted with protons at low temperatures. Two DLTS signals, labeled ${E3}^{\ensuremath{'}}$ and ${E3}^{\ensuremath{''}},$ originate from hydrogen-related donor centers. The electron emission rates of the donors are similar and the two signals are discernible only because they form and anneal differently. In n-type silicon, the ${E3}^{\ensuremath{'}}$ and ${E3}^{\ensuremath{''}}$ centers transform into negatively charged centers at \ensuremath{\sim}100 K and at \ensuremath{\lesssim}65 K, respectively. Both signals can be regenerated at 65 K: ${E3}^{\ensuremath{'}}$ by forward-bias injection of holes and ${E3}^{\ensuremath{''}}$ by illumination with band-gap light under reverse-bias conditions. During the ${E3}^{\ensuremath{'}}$ regeneration long-range migration of hydrogen occurs, whereas ${E3}^{\ensuremath{''}}$ regenerates without migration. In the space-charge layer of reverse biased diodes, ${E3}^{\ensuremath{'}}$ converts into ${E3}^{\ensuremath{''}}$ with an activation enthalpy of 0.44 eV in oxygen-rich material, whereas ${E3}^{\ensuremath{''}}$ converts into ${E3}^{\ensuremath{'}}$ with an activation enthalpy of 0.72 eV in oxygen-poor material. It is found that the density of hydrogen sites associated with ${E3}^{\ensuremath{''}}$ approximately equals the oxygen concentration, whereas the density of ${E3}^{\ensuremath{'}}$ sites is about ${10}^{23}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}.$ These results provide further evidence for our previous assignment of ${E3}^{\ensuremath{'}}$ to isolated hydrogen at a bond center site and leads to the assignment of ${E3}^{\ensuremath{''}}$ to bond centered hydrogen perturbed by a nearby oxygen atom. We argue that dilated Si-Si bonds in the strain fields around impurities and defects are trapping sites for hydrogen.

It is found that shallow hydrogen-related donors are formed in the proton-implanted dilute Ge 1 − х Si х alloys (0 ≤ x ≤ 0.031) as well as in Si-free Ge samples upon heat-treatments in the temperature range 225–300 °C. The maximum concentration of the donors is about 1.5 × 10 16 cm − 3 for a H + implantation dose of 1 × 10 15 cm − 2 . The temperature range of formation of the proton-implantation-induced donors is the same in Ge 1 − х Si х samples with a different Si concentration. However, the increase in Si content results in a decrease of the concentration of the H-related donors. The possible origin of the H-related donors and mechanisms of Si-induced suppression of their formation are discussed.

Proton implantation into n-type silicon at initiates the formation of two deep donor centers containing hydrogen. These centers, denoted E3′ and E3′′, can be observed when deep-level transient spectroscopy is applied in-situ to as-implanted diodes . The emission rates of E3′ and E3′′ are very similar, and the centers are discernible only because they form and anneal differently. In their neutral charge states (i.e. zero-bias annealing) E3′ anneals in ≈10 min at 100 K and E3′′ anneals in ≈50 ms at 75 K. The zero-bias anneals lead to a negatively charged center from which both E3′ and E3′′ can be recovered at low temperature: E3′ by forward-bias injection of holes, and E3′′ by reverse-bias illumination with band-gap light. The E3′ recovery is associated with fast migration of hydrogen, while E3′′ recovers instantly without migration. The analogous anneals in the positive charge states (i.e. reverse-bias annealing) differ for oxygen-rich and oxygen-poor material. In Cz silicon E3′ converts at ≈220 K to E3′′ which then subsequently anneals at ≈260 K. In Fz silicon the order of anneals is reversed. Here E3′′ converts to E3′ at ≈230 K. Both centers disappear in the temperature range 240–260 K. We analyze the annealing scenario within a quantitative diffusion model that complies with the present theoretical understanding of isolated hydrogen in silicon. We conclude that the density of hydrogen sites associated with E3′′ approximately equals the oxygen concentration while the density of E3′ sites corresponds to the atomic density of silicon. We identify the E3′ center as isolated bond-center hydrogen and E3′′ as bond-center hydrogen which is perturbed (and stabilized in the positive charge state) by nearby interstitial oxygen. We argue that dilated Si–Si bonds, present in the strain field around impurities and defects, rather generally may act as trapping sites for otherwise isolated hydrogen resulting in the formation of a family of bond-center type centers that are very much alike.

The Hartree-Fock cluster procedure was used to obtain the associated electronic distributions for 19F* (I = 5/2, E x = 197 KeV excited nuclear state of the 19F atom) at possible sites in crystalline Si, Ge and diamond and to calculate nuclear quadrupole coupling constants v Q and the asymmetry parameter η of the electric field gradient at the modelled sites. Lattice relaxation effects have been incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The intrabond (IB), antibonding (AB) and substitutional (S) sites in the bulk and the atop site on the surface were studied. From a comparison with v Q and η values observed in time differential perturbed angular distribution (TDPAD) measurements we were able to identify the high frequency component in Si and Ge with 19F* at the intrabond site. In diamond two high frequency components are observed. These are identified with 19F* at intrabond and substitutional sites. For the low frequency site in Si and Ge the assignment is made to 19F* implants at dangling bonds in the bulk resulting from implantation damage. In diamond none of the sites studied could provide lower frequency nuclear quadrupole parameters close to the observed ones.

In the present investigation, we have made use of our newly produced n+p-mesa diodes on Ga-doped, 2-Ω cm Ge-single crystals to study irradiation-induced defects in p-type Ge. Irradiation with electrons shows five distinct levels introduced. The use of protons and α-particles (and at different doses) for irradiation, reveals four new levels, and allows for the possibility of connecting some of the levels to the divacancy.

Using the Hartree-Fock-Roothaan procedure the nuclear quadrupole interactions of the19F (spin 5/2) nucleus in CF4, SiF4 and GeF4 are studied. The theoretical results explain within 10% the observed experimental measurements by the time-differential perturbed angular distribution technique, including the important feature of sharp decrease of the19F* nuclear quadrupole coupling constant in going from CF4 to SiF4, followed by an increase in going to GeF4, while a simple consideration of the ionic characters of the C-F, Si-F and Ge-F bonds together with Townes and Dailey theory would lead to a continuous decrease from CF4 to GeF4. The dependence of the results on the choice of basis sets and the role of many-body effects is discussed.

The diffusion of platinum into lightly damaged regions of ion‐implanted silicon has been investigated using deep‐level transient spectroscopy and capacitance‐voltage profiling. The samples consisted of PtSi/Si n‐type Schottky diodes which had been implanted with O, F, or Cl to an intermediate depth between the zero‐bias and reverse‐bias depletion boundaries, and subsequently annealed at a temperature of 700 °C. The distribution of in‐diffused Pt was obtained by monitoring the electron emission from the acceptor level (EC−ET=0.23 eV) previously assigned to Pt in a distorted substitutional configuration. The Pt was found to be distributed approximately congruous with the vacancy distribution generated during implantation. For a typical implantation dose (≊1011 cm−2) we recorded an enhanced accumulation of Pt by about two orders of magnitude as compared to diffusion into nonimplanted material. This apparent decoration of the primary damage profile occurs without the simultaneous introduction of other electri...

This paper is to commemorate the work of Leszek Dobaczewski 1 who devoted much of his life to the development and application of high resolution DLTS. Under good experimental conditions Laplace DLTS provides an order of magnitude higher energy resolution than conventional DLTS techniques. This has had a profound effect on electrical defect spectroscopy enabling the effect of external probes, such as uniaxial stress, and internal perturbations, such as the proximity of atoms isovalent with the host, to be quantified in terms of electronic behaviour. Laplace DLTS provides a synergy with other techniques that was difficult or impossible to achieve previously. In this paper we present an overview of the development of LDLTS and illustrate some of its uses by describing its application in a number of key areas of defect research. Leszek Dobaczewski was born on 25th December 1954. He received his education in Warsaw taking his PhD in 1986 with Jerzy Langer at the Institute of Physics on Recombination Processes at defects with the large lattice relaxation. He held a research position at the institute in Warsaw until he came to Manchester in 1990 and thereafter alternated between Manchester and Warsaw. He worked primarily on the development and application of high resolution DLTS. He was awarded the degree of DSc in 1994 for his work on DX centres and held an appointment as full professor in Warsaw with Visiting Professor posts at Manchester and Aarhus. © 2011 Elsevier B.V. All rights reserved.

This paper is to commemorate the work of Leszek Dobaczewski1 who devoted much of his life to the development and application of high resolution DLTS.Under good experimental conditions Laplace DLTS provides an order of magnitude higher energy resolution than conventional DLTS techniques. This has had a profound effect on electrical defect spectroscopy enabling the effect of external probes, such as uniaxial stress, and internal perturbations, such as the proximity of atoms isovalent with the host, to be quantified in terms of electronic behaviour. Laplace DLTS provides a synergy with other techniques that was difficult or impossible to achieve previously. In this paper we present an overview of the development of LDLTS and illustrate some of its uses by describing its application in a number of key areas of defect research.Leszek Dobaczewski was born on 25th December 1954. He received his education in Warsaw taking his PhD in 1986 with Jerzy Langer at the Institute of Physics on “Recombination Processes at defects with the large lattice relaxation”. He held a research position at the institute in Warsaw until he came to Manchester in 1990 and thereafter alternated between Manchester and Warsaw. He worked primarily on the development and application of high resolution DLTS. He was awarded the degree of DSc in 1994 for his work on DX centres and held an appointment as full professor in Warsaw with Visiting Professor posts at Manchester and Aarhus.

The nuclear quadrupole interaction parameters e 2 qQ and η are calculated for fluorine nuclei in fluorobenzenes from wave functions obtained using a first-principles Hartree-Fock procedure utilizing linear combinations of atomic orbitals. Weighted averages of these individual parameters are used in an attempt to explain results obtained from time-dependent perturbed angular distribution measurements made earlier on various fluorobenzene samples implanted with 19 F * . Six different basis sets were used. Agreement between the calculated and experimental results for e 2 qQ was within 16% in all cases and within 3% for two of the basis sets used, and the trend in e 2 qQ with increasing fluorinesubstitution was successfully predicted

The first results demonstrating the existence of a donor level of interstitial hydrogen in CdTe are presented. From the Arrhenius analysis, this donor level is characterized by an activation energy for electron emission ${E}_{\text{C}}\ensuremath{-}{E}_{\text{t}}=0.06\text{ }\text{eV}$ and a pre-exponential factor equal to $2\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }{\text{s}}^{\ensuremath{-}1}\text{ }{\text{K}}^{2}$, and is observed after a low-temperature implantation with protons. Above 75 K the hydrogen-deep donor state is unstable converting to a more stable configuration which is believed to be a negatively charged form of isolated H. The results are analogous to what has been observed for interstitial hydrogen in GaAs.

The electronic properties of defects resulting from electron irradiation of germanium at low temperatures have been investigated. The recent success in preparing ${n}^{+}p$ junctions on germanium has opened a new opportunity to address fundamental questions regarding point defects and their related energy levels by allowing an access to the lower half of the band gap. In this work we apply various space-charge capacitance-transient spectroscopy techniques connected on line with the electron-beam facility. In $n$-type germanium we identify a level at about 0.14 eV below the conduction band whose properties resemble in many respects those of a defect assigned previously to the close vacancy-interstitial or Frenkel pair. This pair seems to annihilate over a small barrier at about 70 K, and its stability is particularly sensitive to the irradiation temperature and energy. We also observe two coupled levels at 0.08 and 0.24 eV below the conduction band stable up to 160 K. Recent independent theoretical work has predicted the existence of the single and double donor of the germanium interstitial with energy levels matching exactly these two values. Given these identifications hold, they mark a major difference with silicon where both the Frenkel pair and self-interstitial have never been caught. In $p$-type germanium, two levels were found. The shallower one, located at about 0.14 eV above the valence band, is tentatively assigned to the vacancy. It exhibits a field-driven instability at about 80 K making its analysis quite difficult. The application of a reverse bias, required by the space-charge spectroscopy, leads to a strong drift process sweeping this defect out of the observation area without necessarily provoking its annealing. Unlike silicon, in which the vacancy has four charge states, only one vacancy-related level seems to exist in germanium and this level is very likely a double acceptor. Finally, a very peculiar observation is made on a hole midgap trap, which, in many respects, behaves as the boron interstitial in silicon. This has led us to suggest that it may stem from the gallium interstitial, a natural dopant of our germanium materials, whose presence would be the fingerprint of the Watkins replacement mechanism in germanium.

We identify the donor level of interstitial hydrogen in GaAs, which is characterized by the activation enthalpy E{sub C}-E{sub t}=0.13 eV. This level is the marker of two different but closely related defect structures, which are indistinguishable as far as their emission properties are concerned; however, discernible on the basis of their different dynamical behaviors are revealed by annealing studies. We interpret the two structures as regular bond center hydrogen H(BC) and bond center hydrogen H(BC{sup '}), which is perturbed by the local strain from a neighbor point defect. We demonstrate negative-U properties of the perturbed structure and infer that the corresponding acceptor H(T{sup '}) lies deep in the band gap. These results for interstitial hydrogen in GaAs are in every aspect analogous to the properties of interstitial hydrogen in Si.

We have studied n-type silicon containing gold and gold–hydrogen complexes using high-resolution “Laplace” deep-level transient spectroscopy. This technique has enabled two quite distinct electron emission rates to be observed at temperatures between 240 and 300 K. These are associated with the gold acceptor and the level referred to as G4, which is observed when hydrogen and gold are present in silicon. The gold acceptor has a measured activation energy for electron emission of 558±8 meV, and the G4 state of 542±8 meV. The directly measured electron capture cross section for G4 is determined to be 0.6±0.1 σn(gold acceptor) at 275 K from which it is inferred that the state is acceptor-like.

In this report we present high-resolution spectra obtained with a use of the Laplace transform deep level transient spectroscopy for platinum diffused into dilute (0-5% of Ge) SiGe alloys. Very significant changes are observed in the spectra associated with the transition metals as the germanium content is altered. We interpret these spectra in terms of the configurations of silicon and germanium atoms surrounding the transition metal. In order to explain the observed behaviour both the first and second nearest neighbour shells are considered.

It has been an accepted fact for more than 40 years that the $E$ center in Si (the group-$V$ impurity---vacancy pair)---one of the most studied defects in semiconductors---has only one energy level in the band gap: namely, the acceptor level at about 0.45 eV below the conduction band. We now demonstrate that it has a second level, situated in the lower half of the band gap at 0.27 eV above the valence band. The existence of this level, having a donor character, is disclosed by a combination of different transient-capacitance techniques and electronic-structure calculations. The finding seriously questions some diffusion-modeling approaches performed in the past.

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In this study, we used n(+)p mesa diodes where the highly arsenic doped n(+) top layer was grown by molecular-beam epitaxy on top of a 5-mu m thick p-type layer grown by chemical-vapour deposition. The diodes were irradiated with 2 MeV electrons at room temperature and the resulting defects in the p-type region were studied by Laplace and standard deep-level transient spectroscopy. A new defect with an apparent energy position of 0.20 eV above the valence band is shown to migrate from the n(+) top layer into the p-type material where it is observed by DLTS. An annealing study shows that this defect grows in at similar to 400 K and disappears at similar to 460 K. We argue that this defect is the AsV complex, and that it is formed in the top layer when negatively charged AsV pairs, which are generated in the n+ top layer by the electron irradiation, migrate and react with the abundant and positively charged As donors. Once formed, the AS(2)V complex diffuses into the p-type material.

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Deep‐level transient spectroscopy has been combined with ion implantation in low‐temperature investigations of deep centers in silicon. We demonstrate that thermal radiation, originating from vacuum chamber walls, can influence in situ recording of emission rates significantly. As an example, the emissivity (en) of the hydrogen E3′ center was found to be dominated by an optical contribution at temperatures below ≊65 K. A typical value, en(op)≊5.5 s−1, has been recorded in measurements with unshielded Au Schottky diodes. This effect of thermal radiation vanishes when a diode is fully encapsulated and thereby in thermal equilibrium with the radiation field. The optically induced emissivity is particularly large for the hydrogen center used here to illustrate the effect but has been observed for other deep centers as well.

A shallow fluorine‐related donor is reported. The donor has been revealed by capacitance–voltage profiling applied to furnace‐annealed, fluorine‐implanted silicon samples. The implantations were carried out at high energy, in the range 5–7 MeV. The assignment of the donor structure to fluorine results from a detailed examination of the effective space‐charge distribution around the implantation range (≊4 μm) in comparison with data obtained for similar oxygen‐implanted samples. The depth‐integrated density of the donors formed after annealing at 700 °C is ≊3×1010 cm−2 corresponding to ≊1% of the implantation dose. The density increases by more than one order of magnitude for samples annealed only at 600 °C. In addition to the shallow donor level (or levels) a fluorine‐specific level at Ec−Et≊0.15 eV has been assigned by application of deep‐level transient spectroscopy.

We apply Laplace deep-level transient spectroscopy (LDLTS) in situ after low-temperature proton implantation into crystalline $n$-type germanium and identify a deep metastable donor center. The activation energy of the donor emission is $\ensuremath{\sim}110\phantom{\rule{0.3em}{0ex}}\text{meV}$ when extrapolated to zero electric field. We obtain the split patterns of the emission signal for uniaxial stress applied along three major crystal directions $⟨100⟩$, $⟨110⟩$, and $⟨111⟩$, and conclude that the symmetry of the center is trigonal. We compare the annealing characteristics with those of bond-center hydrogen in silicon and with those of a trigonal center in germanium previously identified as bond-center hydrogen by in situ local-mode infrared absorption spectroscopy. From this comparison it is concluded that the observed donor emission originates from bond-center hydrogen. Infrared absorption also revealed another trigonal center tentatively ascribed to hydrogen occupying an antibonding configuration. A search for a corresponding deep level (as a hole or electron trap) failed, indicating that such level must be near midgap or resonant with (close to) the valence band.

A process‐induced metastable defect in n‐type silicon is reported. The defect is found close to the wafer surface after combination of ambient gas‐flow annealing at ≊900 °C depending on subsequent cleaning procedure. The defect gives rise to a band‐gap level Ec−Et=0.25 eV observed by deep‐level transient spectroscopy after reverse‐bias cooling of the sample. Both annealing and generation of the defect proceed by 1st order processes. The activation enthalpies (ΔE) and pre‐exponential factors (v) have been determined from Arrhenius analyses; the results are ΔE=0.63 eV and ν=1⋅1012 s−1 for annealing, and ΔE=0.65 eV and ν=6⋅1014 s−1 for generation.

The piezospectroscopic properties of the $V\mathrm{OH}$ defect in Si are found using stress Laplace deep level transient spectroscopy (DLTS) and are compared with local density-functional calculations of (i) the acceptor level and its shift under stress, and (ii) the alignment of the neutral center under stress. The theory is able to account for two acceptor levels observed for $〈100〉,$ $〈111〉,$ and $〈110〉$ stress even though additional splitting is expected for a defect with static ${C}_{1h}$ symmetry. This is related to (i) a rapid reorientation of the H atom within the defect at temperatures at which the DLTS experiments are carried out, and (ii) the small effect of stress on two orientations of the defect under $〈110〉$ stress. The theory is also able to give a quantitative account of the alignment of the center. The effect of stress on the reorientation barrier of the defect is also investigated. The reorientation barrier of the defect in its positive charge state is found theoretically to be very small, consistent with the lack of any splitting in the donor level under stress.

We apply Laplace deep-level transient spectroscopy in situ after low-temperature proton implantation into dilute Si 1 - x Ge x alloys and identify the deep donor state of hydrogen occupying a strained Si-Si bond-center site next to Ge. The activation energy of the electron emission from the donor is ∼158 meV when extrapolated to zero electrical field. We construct a configuration diagram of the Ge-strained site from formation and annealing data and deduce that alloying with ∼1% Ge does not significantly influence the low-temperature migration of hydrogen as compared to elemental Si. We observe two bond-center-type carbon-hydrogen centers and conclude that carbon impurities act as much stronger traps for hydrogen than the alloy Ge atoms.

A piezospectroscopic analysis of the vacancy-oxygen complex in silicon has enabled us to demonstrate that this defect in the unstable configuration of the saddle point on the reconfiguration trajectory has a trigonal symmetry. This unstable defect configuration may be considered as the precursor for an oxygen diffusion process where the migrating oxygen atom is accompanied by a vacancy. The trigonal saddle point configuration results in a strong electrical polarization of the pair which can aid the jumping to a neighboring unit cell. This scenario is very plausible to explain how vacancies can drag oxygen atoms through the crystal to form larger oxygen aggregates.

It is shown that the divacancy in silicon in the diamagnetic doubly negative charge state has a static trigonal symmetry with inward breathing mode lattice relaxation. There is no measurable Jahn-Teller effect, unlike other charge states of the defect. This conclusion has been drawn from an analysis of the piezoscopic characteristics of the complex derived from high-resolution (Laplace) deep-level transient spectroscopy.

We determine the activation enthalpies for electron emission of two near T-site hydrogen centers in silicon to be ;0.65 and ;0.79 eV. The deeper center is oxygen related, and stabilized with a binding energy of ;0.5 eV with respect to the shallower center. We verify the negative-U behavior of both centers, and demonstrate the crucial role that this behavior and the presence of oxygen have for the migration of hydrogen in silicon. The shallower center is interpreted as the acceptor of monatomic isolated hydrogen, and the deeper center is interpreted as a perturbed version of this acceptor.

High-resolution Laplace deep-level transient spectroscopy spectra for gold- or platinum-diffused SiGe samples show an alloy splitting that is associated with the alloy fluctuations in the proximity of the defect. For the case of the platinum acceptor state, the effect of the level splitting caused by alloying in the first and also in the second shell of surrounding atoms can be distinguished. For the case of the gold acceptor, only the effect from the first shell of atoms is observable but the manifestation of alloying in the second-nearest shell can be seen as line broadening. We have found that the electronic energy level is affected by alloying in the first-nearest neighborhood by a factor of 2--3 more than by alloying in the second-nearest shell. The absolute values of the energy differences obtained from the Arrhenius plots for different defect configurations agree with those inferred from the peak separations observed in the spectra. A clear preference for gold and platinum to enter substitutional Si sites adjacent to Ge has been revealed. This may be interpreted in terms of an enthalpy lowering as a result of the fact that both metals are able to replace the host silicon atom more easily than the germanium atom in the substitutional position.