The effect of hydrogen treatment at 200°C on the concentration of electrically active defects in LPE grown AIGaAsSb is reported. In n-type layers the electrical properties are shown to be dominated by DX-like deep donors of three different types all of which are strongly passivated by the hydrogen treatment as evidenced by C-V. DLTS C-T and spreading resistance measurements. In p-type layers intrinsic acceptors of defect origin are also passivated by hydrogen. Deuterium profiles in both n- and p-type layers show characteristic plateaus indicative of formation of neutral compexes between hydrogen and dopants. Hydrogen treatment also leads to decrease of the Au/n-AIGaAsSb Schottky barrier height from 1.3 to 0.85 eV.

Perturbed Angular Correlation (PAC) and Hall measurements were used to investigate the stability of the passivating Cd-H complex in GaAs after low energy H implantation (150 eV, 1014 cm−2) at 300 K. From the observed Cd-H pair formation and reduction of hole concentration it is deduced that about 10 % of the implanted H atoms form pairs with the Cd atoms. The influence of the dopant depth profile on the apparent stability in zero bias isochronal annealing experiments is reported. After H loading a reduction of carrier mobility is observed, which is stable up to about 400 K. The formation of Cd-H pairs after low energy H implantation into InP was studied by PAC. By measuring the fraction of pairs in an isochronal annealing experiment, the stability of the pairs is deduced yielding a dissociation energy of ED = 1.8 (1) eV.

The effect of hydrogen plasma on the electrical properties of low-temperature-grown GaAs (LT-GaAs) is reported. LT-GaAs epitaxial layers, 2μm thick were grown on a <100>, semi-insulating GaAs (SI GaAs) substrate using molecular beam epitaxy (MBE) at 300°C. Some of the samples were annealed in- situ at 600°C for 1 hour. These LT-GaAs samples were then subjected to hydrogen plasma at 300°C in a parallel-plate, low-frequency (30KHz) system for varying times up to a maximum of 13 hours. Current through the LT-GaAs layers as a function of voltage (I-V), temperature (I-T), and time (I-t) was measured between two surface contacts formed by thermal evaporation of Au. Evidence of partical defect passivation found in the electrical characteristics of hydrogenated LT GaAs is presented. These include reduced current at low temperature (<210K) and reduced current activation energy at high temperature (>320K).

We report nuclear magnetic resonance measurements of deuterone diffused into silicon powders. Deuterium spectra show a two-component lineshape corresponding to two distinct hydrogen sites. The component with a narrow Lorentzian lineshape is assigned to D2 molecules. The second component is a quadrupolar doublet powder pattern, and its characteristic splitting provides a value of the electric field gradient at the site of the deuterium atom of 1.45×105 dyn/cm.

The passivation and reactivation of As donor dopants in n-type Si was studied with both monatomic hydrogen and deuterium. Hydrogenated Schottky diodes were characterized with C-V and DLTS measurements. The reactivation kinetics of the As-H and As-D complexes were studied in the space-charge layer of reverse biased diodes in the temperature range from 60°C to 120°C. These bias-anneals yield dissociation time constants for As-H, from which an averaged activation energy of 1.17±0.1 eV was determined. Although the dissociation of the As-H complex is appreciably slower than that previously measured for P-H, the activation energy is within about 0.05 eV of that determined previously for the P-H complex (1.2 eV). The depth redistribution of the As-H complexes after bias-annealing agrees with the previous conclusion that hydrogen can assume a negative charge state in n-type Si.

This paper demonstrates a unique action of hydrogen on defects and impurities in semiconductors. Hydrogen injected into n-type Si by chemical etching or hydrogen plasma not only pas-sivatcs phosphorus but also electrically activates carbon by forming a H-C complex acting as an electron trap E3 (0.15). A model of the structure and electronic state of the H-C complex is proposed on the basis of available experimental data on the properties of the complex. The diffusion coefficient of isolated hydrogen below 300K is evaluated from its diffusion process to phosphorus after the photoinduccd dissociation of the H-C complex. Some differences in hydrogen diffusion between chemically etched and plasma hydrogenated crystals arc discussed.

Deactivation of silicon dopants by hydrogen in GaAs and GaAlAs proceeds through the formation of hydrogen-dopant complexes with thermodynamical and vibrational characteristics weakly sensitive to the alloy composition. However the hydrogen diffusion profile is strongly sensitive to the alloy composition. In GaAs:Si, the profile is an erfc function while in Ga1-xAlxAs:Si with x > xo, it is rather a step like function. From the doping level dependence of xo, we explain the hydrogen diffusion properties within a model where H° and H- govern the diffusion profiles respectively for x < xo and x > xo. We deduce that hydrogen behaves as a deep acceptor in these materials with a level slightly resonant in the conduction band of GaAs and localized in the band gap of Ga1-xAlxAs alloys for x > 0.07.

The formation of Ga-vacancy/hydrogen complexes in GaAs has been detected via photoluminescence measurements. Different degrees of hydrogénation can be achieved by low-energy H- or D-ion irradiation from a Kaufman source. The volume incorporation, for equal treatment, is dependent upon the density of impurities and defects where H can bind. In originally p-type MBE-GaAs, prolonged hydrogen treatments lead to the appearance of three emission structures in the range 1.15–1.34 eV. The results are explained in terms of transitions to different states of charge of gallium vacancies trapping one or more H-atoms, the activity of the individual states being dependent upon the H-dose and the nature of the laser excitation. The model is supported by comparison with the changes in the Ga-vacancy/donor emission band in degenerate n-type samples, as it evolves, from the virgin condition, through hydrogenation. The present observation provides also valid support to the creation, in p-type material, of a semi-shallow donor associated to H trapped along the As-Ga bond, in the immediate neighborhood of the gallium vacancy.

S1O2 layers, ∼ 15 nm thick, were formed on Si (100), (110), and (111) surfaces by a low-temperature, 200–300°C, plasma-assisted oxidation/deposition process sequence. The distribution of the trap density at the S1O2/Si interface, and in the Si band-gap, Dit, was deduced from capacitance-voltage, C-V, measurements. The values of Dit at midgap varied with crystal orientation in a similar way as in thermally grown oxides. In addition, the low-temperature oxides displayed a characteristic and intrinsic dangling bond state, the so-called Pb center, at ∼0.3 eV above the Si valence-band edge. Samples exposed to atomic H prior to the oxidation and deposition steps, showed an increase in Dit due to a roughening of the Si surfaces, which produced additional broad bands of defect states, at ∼0.5 and ∼0.7 eV above the Si valence-band edge.

To reduce the density of recombination centers, external gettering by phosphorus diffusion from a POCI3 source and hydrogénation were applied to 200 μm thick samples.

Gettering was carried out at 850°C or 900°C, for 120 or 240 mn. Hydrogénations result of the annealing of samples at 400°C for 30 mn in gas flow. Thanks to arrays of mesa diodes, it is found that minority carrier diffusion lengths (Ln) are neatly improved by the gettering. The improvements are higher at 900°C than at 850°C, they increase with gettering time and SIMS analyses indicate that they are due to the removing of Fe, Cu and Ni atoms.

Hydrogénation enhances Ln values in samples gettered at 850°C and the higher Ln the longer the gettering time. After hydrogénation, the values of Ln in the samples gettered at 850°C are comparable to those measured in samples gettered at 900°C. It is assumed that hydrogen is able to neutralize the activity of impurities which have not been gettered, like oxygen, and also that of residual metallic impurities.

Recent studies of the deep transition-metal centers Ti, V, Mo and W in silicon are discussed, which have been investigated using junction-space charge techniques. The changes in the Gibbs free energy, enthalpy, and entropy due to electron or hole excitation of these transition metal related levels are presented. The good agreement of the Gibbs free energies with the optical threshold energies of the corresponding photoionization cross sections suggests negligible lattice relaxation. For the Ti-doped samples three energy levels at Ec-0.065 eV, Ec-0.295 eV and Ev+0.255 eV at 80 k were observed. For Mo and W the energy levels are located at Ev+0.298 eV and Ev+0.379 eV, respectively, at 80 K. Three energy levels of the V-related centers exist at Ec-0.207 eV, Ec-0.483 eV and Ev+0.356 eV at 0 K. A structure in the low-energy part of the spectral distribution of the level Ec-0.483 eV is assumed to be due to excited states and shown to be in good agreement with effective-mass theory. Previous assignments of the energy levels should be reconsidered.

Using deep level transient spectroscopy (DLTS) on gold-doped n-type Czochralski (CZ) and float zone (FZ) silicon we observe a new gold-related acceptor level (G) with an activation energy σn= 0.19 eV and an electron capture cross section On = 1–10-17 cm2. The center anneals out at a temperature of 250°C, simultaneously as the gold acceptor concentration increases. Annealing at temperatures below 250°C does not reverse this process. However, etching a few microns off the sample surface using HF:HNO3 based etch reforms the G center and the gold acceptor concentration decreases accordingly. From DLTS depth-profiling we determine that the new center is only found at depths less than 5 μm, and in the same region we observe neutralization of phosphorus dopants and a reduction in the gold acceptor concentration.

We propose that in-diffusion of hydrogen during the etching process is responsible for the three observed transitions, i.e. neutralization of both phosphorus donors and gold acceptors and formation of the G center. We suggest that there are (at least) two possible Au-H complex centers, one which is electrically inactive and another which gives rise to an acceptor level (ΔE = 0.19 eV) in the bandgap of n-type silicon. The electrically active center anneals out at 250°C while the electrically inactive one is more stable and has been observed earlier in remote plasma hydrogenation experiments performed at 150–350°C.

For the first time the acceptor state of iron-boron pairs the occurence of which are suggested by electrical measurements and theoretical considerations is directly proved by EPR measurements. The corresponding EPR spectrum is observed upon suitable illumination of samples which have been co-doped with boron and iron. It shows trigonal symmetry, and the fine-structure pattern can be described with the spin S = l, the g-values gi ∼ 2.1345±0.0001, gi = 2.1345±0.0004 and the zero-field splitting parameter |D| = (1.418±0.001) cm−1.

In this paper we analyze processes which may improve the efficiency of low- and high- field electroluminescence devices based on rare earth doped II-VI and III-V semiconductors. The main topicsare the processes which follow impact ionization, i.e., carrier trapping and/or exciton binding. Excitonic excitation mechanism is shown to occur also for ions which are not directly ionized, as observed recently for some rare earth impurities in II-VI and III-V semiconductors.

Stable forms of donor-acceptor pairs in silicon arise from the interaction between negatively charged acceptors and 3d transition element donors, which, occupying interstitial sites, have high mobilities. The atomic and electronic structure of these pairs can be studied in detail by magnetic resonance. The symmetry of centers as observed in the resonance experiments gives strict constraints on the applicable atomic models. The spin of centers is related to their charge state. Hyperfine interactions frequently lead to a specific structure in the spectra, which characterizes the chemical identity of atomic components of the pair. Deep level transient spectroscopy provides a way of sensitive observation of electrically active impurities: to determine their concentrations and associated electronic levels. It allows the study of the kinetics of the pair formation process and thermally induced dissociation; binding energies can be determined. Transformation of pairs as a result of illumination was also observed. Several of the pairs can exist in geometrically different atomic configurations leading to the phenomenon of bi- or multi-stability. In the paper the donor-acceptor pair formation process is illustrated by examples involving the substitutional double acceptor zinc, for which new data became recently available.

We propose a generalized model for gold diffusion in silicon based on the effect of the high concentrations of vacancies and vacancy complexes in the as-grown silicon. The monovacancy profiles calculated using this model are identical to the substitutional gold profiles calculated using the kick-out model. We deposited Au on commercial float zone Si in a vacuum system after the Si had reached the diffusion temperature (1233 K) and had been annealed in various ways. Contrary to previously published reports, we find the electrically active Au with a nearly one-sided profile when the Au is deposited on samples which were preannealed in vacuum. We conclude that annealed silicon surfaces lack the imperfections needed to make them effective sources or sinks for vacancies or self-interstitials. We propose that this can cause a high degree of supersaturation in the as-grown silicon crystal since the point defects cannot annihilate at the surfaces to maintain equilibrium as the crystal is cooled.

Highly officient radiative recombination even at room temperature was found at a wavelength of about 1.3 μm in heat-treated Si-doped GaAs. The range of Si concentrations and the condition of heat-treatment to yield this intense luminescence were determined. Excitation spectra of the PL lines suggest that such PL lines are related to pairs of Si-donor and Si- acceptor and such pairs combined with gallium vacancies.

Wc have found that chemical etching induced an electron trap E3 (0.15) into n-typc Si. We attribute this trap to a hydrogen-carbon complex on the basis of available experimental data. By measuring DLTS depth profiles of the E3 trap, we propose a model of the formation mechanism of the hydrogen-carbon complex as follows. Hydrogen atoms arc adsorbed on the Si surface to terminate Si dangling bonds during chemical etching, and after the etching some unstably adsorbed ones diffuse into the near-surface region of silicon and are trapped by carbon to form the complex. The E3 trap is stable up to 100δC in the dark but is annihilated by the illumination of band gap light around 250K only outside the depletion layer of the Schottky structure. This provides unambiguous experimental evidence for the recombination-enhanced dissociation, in which the electronic energy released by the electron-hole recombination at the E3 level is converted into local kinetic energy of hydrogen to be released from carbon.

We have found configuratlonally metastable Fe-B pairs in Si by using dark or photo capacitance-transient technique combined with minority-carrier injection. The metastable pairs are observed as four electron-trapping levels at Ec-0.43 eV, 0.46 eV, 0.52 eV, and 0.54 eV and as two hole-trapping levels at Ev+0.53 eV and 0.48 eV after the injection at 150 K. The production of each level is investigated under various injection conditions, and the annihilation process is studied by isochronal anneals.

The process physics of the iron-boron pair recombination and dissociation in p-type silicon at temperatures below 300°C was studied. The result indicates that the recombination and dissociation processes depend strongly upon the relative position of the ionization energy of interstitial iron Efe+ and the Fermi level Ef. At temperatures T < (Efe+ - Ep)/k, the pairing reaction obeys first-order reaction kinetics while at temperatures T > (EFe+ - Ep)/k, an equilibrium between neutral and charged defect species prevails.