New data are presented that considerably strengthen the conclusion, reported previously, that hydrogen can passivate shallow donors in silicon by associating with them to form neutral complexes. Effects of inhomogeneity of doping with depth have been eliminated in the new experiments; the observed increase of the effective Hall mobility after hydrogenation requires neutralization of ionizeddonor scattering centers.

Infrared spectroscopy has been used to study hydrogen passivation of P, As, and Sb donors in Si. The spectra show several new absorption bands due to donor-H complexes. By comparing spectra after different heat treatments it is shown directly that the passivation is due to complex formation.

Hydrogen injection with B acceptor neutralization in p-type Si etched in HNOs and HF acid mixtures has been confirmed by isotopic [D] substitution and secondary ion mass spectrometry [SIMS] profiling. Quantitative measurements of the near-surface Injected hydrogen were made following field-aided, in-bulk transport [H+ drift] in reverse-bias annealed Schottky diodes from etched, B-doped Si. Chemical-etch injection is found to be self limiting with neutralization observed over a depth which is characteristic of the base material acceptor concentration and in the range 6–8 extrinsic Debye lengths, indicating that holes are essential in the injection mechanism. An effective diffusivity for hydrogen in etched p-Si of ∼ 2 × 10−9 cm2 s−1 was measured [300 K], considerably higher than previously reported.

The chemomechanical polishing mechanism is described as a corrosive attack of water forming Si-H and Si-OH groups. By adding ammonia or amines to the slurry we observe an irlfease of the resistivity corresponding to a neutralization of up to 1 × 1017 acceptor atoms cm−3 in the case of p-type silicon, whereas n-type silicon can show a slight reduction in resistivity due to the neutralization of the residual acceptor concentration.

SIMS measurements show the presence of hydrogen in the bulk. Using deuterium instead of hydrogen, a correlation could be established between the deuterium content of the wafer, measured by the effusion technique, and the degree of the acceptor compensation.

As can be shown by resistivity and C/V-measurements, under the conditions of polishing the supposed inactivator hydrogen migrates to a distance finally corresponding to the thickness of a wafer. This is contrary to the comm on method of plasma treatment, where a damaged silicon layer is supposed to act as a barrier to the hydrogen diffusion. Differences in the IR spectra can be explained this way.

Crystal imperfections in the bulk and on the surface influences the migration of hydrogen essentially.

Hydrogen ion implantation was performed on Al/n-Si Schottky diodes at doses ranging from 1014 H cm2 to 1016 H cm−2. The effects of ion bombardment and subsequent heat treatments on the diodes were studied using the current-voltage, capacitance-voltage and deep level transient spectroscopy techniques. To explore the stability of hydrogen in silicon, the 1H(15N,aγ)12C nuclear resonance reaction was used. The different effects observed in the low and high dose implantation will be presented.

The paper proves experimentally that no multisilanes are formed even after high temperature proton implantation of crystalline silicon.

The hydrogen depth profiling in the near-surface region in silicon reveals the existence of a subsurface hydrogen layer. This layer acts as a barrier to diffusion. The observed subsurface hydrogen profile rises and then drops off sharply with increasing depth and is stable up to 770 K. Our annealing data indicate a rather complex motion of monatomic and molecular hydrogen in the near-surface region (<1500 A) in the temperature range 300 – 800 K. The subsurface molecule formation represents the dominant hydrogen trapping process in silicon.

The reversible introduction of atomic hydrogen into III–V semiconductors reduces the active concentrations of shallow donor and acceptor levels, as well as a variety of deep levels. Dissociation of the hydrogen-containing complexes by thermal annealing can restore the original active concentrations, and aid in the characterization of the complexes involved. Hydrogen is in-diffused at temperatures typically in the 150 to 300°C range, most simply from an H2 plasma.

In GaAs, the III–V compound which has been subjected to the most hydrogenation studies, carrier concentrations are reduced (by up to many orders of magnitude) in both n- and p-type material. Hydrogen diffusion depths are dependent on dopant concentration, but for similar doping levels, diffusion is always deeper into p-type GaAs. In addition, the type of plasma exposure strongly influences the depth of H diffusion, with low frequency, direct exposure producing the greatest penetration depth. A variety of deep level defects in bulk material (including EL2) and in MBE-grown layers can be passivated, and partial passivation of interface-related defects in GaAs-on-Si has been demonstrated. Reactivation kinetics are dependent on the nature of the dopant or defect, with the passivation of p-GaAs being less stable than that of n-GaAs. Recent infra-red absorption studies have confirmed the formation of a donor-hydrogen complex in n-GaAs, in contrast to an As-H complex in p-GaAs. In GaAIAs, acceptors, donors, and the DX center have been passivated. In some cases, the defect passivation has greater thermal stability than that of the shallow levels, a property of potential benefit. Recently demonstrated applications of hydrogenation include an MBE GaAs MESFET with a hydrogenated channel, and a GaAs/GaAIAs double heterostructure laser with current guiding provided by resistive hydrogenated regions.

We studied the low-temperature photoluminescence (PL) of several III–V compound semiconductors before and after hydrogen-plasma treatment. Drastic intensity changes of the bound exciton luminescence after hydrogen plasma treatments indicate a neutralization of impurities by the atomic hydrogen. In GaP, neutralization of the sulfur donor as well as the acceptors (C, Zn, Cd) is observed. The intense luminescence of the exciton bound to isoelectronic N in GaP is fully quenched by hydrogen plasma treatment.

In order to gain a better understanding of hydrogen in GaAs crystals, a Zn doped p+ GaAs wafer has been implanted with 300 keV protons (H) to a fluence of 1E16/ain and portions of the wafer have been furnace annealed at temperatures up to 600°C. The implanted H and the dopant Zn atomr were then depth profiled using secondary ion mass spectrometry (SIMS). The measurements show that the H redistributes itself in the p+ GaAs(Zn) in much the same manner as it does in n+ GaAs(Si). Movement of the implanted H begins with annealing at 200°C and proceeds rapidly with higher temperatures. However, based on the SIMS profiles, the diffusion coefficient for the H diffusing into the undamaged p+ GaAs(Zn) crystal appears to be considerably higher than that of H into n+ GaAs(Si). Electronic properties of the inplanted and annealed p+ GaAs samples have also been examined and correlated with the SINE profiles.

We show that silicon acceptors can be neutralized in p-type GaAs: Si. SIMS analysis shows that the deuterium concentration closely follows the net acceptor concentration. Infrared absorption spectroscopy reveals lines at 2094.7cm-1 and 1514.5cm-1 in hydrogenated and deuterated samples respectively. The ratio r of the two frequencies is 1.383 indicating that the lines are related to hydrogen isotopes. The reduction of the intensity of the local vibrational mode (LVM) of SiAs after neutralization is consistent with the formation of SiAs-H bonds. From SIMS data, it is concluded that most of the hydrogen present in the passivated material is complexed with silicon. A microscopic model of the Si-H complex is proposed.

Series of sharp optical absorption lines around 2200 cm-1 in GaP, 2000 cm-1 in GaAs, and 2300 cm-1 in InP are observed in bulk materials. They are shown to be due to stretching local modes of vibration of P-H or As-H bonds, the hydrogen sitting nearby an impurity or defect. The origin of the hydrogen contamination of the bulk materials is discussed.

Protons and deuterons have been implanted in n+ GaAs:Si epilayers. Localized vibrational modes (LVM's) associated to H- and D-related defects are observed in the as-implanted samples and they account presumably for the carrier removal in the compensated region, but a small concentration of Si-H passivating centers is already present. LVM spectroscopy shows that after a 200° C annealing, passivation predominates over compensation while a 400° C annealing extends partial passivation throughout the layer.

The arsenic antisite-arsenic interstitial pair model for the stable configuration of the EL2 defect in GaAs has stimulated new experimental and theoretical studies, the results of which lead to additional support for this model. Recent theoretical studies, taking into account the effect of a Jahn Teller distortion of the T2 Asi levels have given an insight into the stability and the electronic structure of the defect pair. Further, ODENDOR studies have directly confirmed this model and allowed one to specify the lattice location and the charge state of the Asi ion. The pair structure of this defect implies a reconsideration of the charge states of the EL2 defect, as well as the origin of the optical absorption bands for which transitions on the Asi ion and intracenter bands have also to be considered. The model leads further to a description of the metastable configuration : an arsenic molecule at the gallium vacancy site, the electronic structure of which is calculated. The vacancy related defects, known from electron irradiation studies, are not detected in LEC grown GaAs as native defects.

With optically detected electron spin resonance (ODESR) and electron nuclear double resonance (ODENDOR) the following deep level defects in s.i. LEC-grown GaAs were investigated: EL2 defects in undoped GaAs and VGa2+ and VGa3+ defects in V-doped GaAs. This paper summarizes the major results: (i) the double donor defect EL2 in an (AsGa-Asi+) pair defect, which is distributed rather homogeneously across an as-grown wafer. After inverted thermal conversion treatment it is destroyed, and 3 new paramagnetic defects appear. EL2 is recovered after annealing at ca. 800 °C, while the 3 new defects disappear. (ii) A new ESR spectrum due to VGa2+ was measured. It is shown for the first time for a 3dn impurity in semiconductors that VGa3+(3d3)is in a low spin state (S = 1/2) in accordance with recent theoretical predictions. A deep level defect at Ev + (0.2–0.4) eV is discovered, which is probably the defect needed for explaining the s.i. properties of V-doped GaAs.

The levels and excitation energies of the weakly interacting AsGa—Asi defect pair have been calculated using the model energy functional introduced by Baraff and Schluter, modified so as to allow Jahn Teller relaxation to distort the Asi away from the symmetry site. The physics underlying this calculation and the results emerging from it are described in this paper. We find that many previously unrelated experimental observations about EL2 are well accounted for by this model. However, there are still some controversial aspects of the fit of the model to the observed properties of EL2 which we cite as requiring further study.

Thermal behavior of midgap defects generated in GaAs by different procedures has been followed by means of optical absorption measurements at low temperature. EL2 centers existing in as-grown crystals or generated by thermal annealing at temperatures lower than about 1000°C, which are characterized by a perfectly quenchable absorption at a wavelength of 1.0 μm, are found to diminish at temperature higher than 1000°C. The generation kinetics of EL2 centers has been traced during isothermal annealing of a crystal in which grown-in EL2 centers have previously been eliminated by annealing at 1200°C. The result of an analysis with the use of simplified chemical rate equations favors the model that an EL2 center is composed of an As antisite and two Ga vacancies. Both quenchable and unquenchable absorptions are associated with the midgap defects induced by plastic deformation or electron -irradiation. Isochronal annealing reveals that such defects are not identical with EL2 centers that are found in an as-grown crystal even if they accompany the quenchable absorption.

We have measured the time resolved transmission of short pulses of ballistic phonons in a GaAs crystal known to contain the intrinsic defect EL2. These measurements were performed for phonons propagating along several high symmetry directions at 2K. Measurements were made both before and after the crystal was irradiated with 1.06 μm light to convert EL2 from its ground state to its metastable state. The changes in phonon transmission measured for the different phonon polarizations and propagation directions lead us to associate a trigonal symmetry with the defect whose phonon scattering has changed. The identification of this defect as EL2 is discussed below.

We have studied, using DLTS, the EL-2 concentration in unintentionally doped OMVPE n-GaAs as a function of growth conditions such as partial pressure of Arsine, Trimethylgallium and growth temperature. The partial pressure dependencies are used to develop a model for the formation of EL-2 in the OMVPE process. The EL-2 concentration also shows a near inverse dependence on growth temperature.

We have studied by means of deep level transient spectroscopy and photocapacitance measurements deep electron traps in undoped Ga1−xAlxAs of n-type grown by metalorganic chemical vapor deposition with 0≤x≤ 0.3. A dominant deep electron trap is detected in the series of alloys. Its activation energy is found at EC-0.8 eV in GaAs and it increases with x. Its concentration is found nearly independent of x. For the first time we observed for this level in the Ga1−xAlxAs alloys, the photocapacitance quenching effect typical for the EL2 defect in GaAs thus confirming clearly that EL2 is also created in MOCVD Ga1−xAlxAs.