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Notes: We have recently found that hydrogen injected into n-type crystalline silicon by chemical etching not only passivated phosphorus but also electrically activated substitutional carbon by forming a hydrogen-carbon complex with a donor level at Ec−0.15 eV. This article shows that the complex was annihilated by above-gap excitation near and below room temperature only outside the depletion layer of the Schottky structure under the application of various reverse bias voltages. This clearly proves that the hydrogen-carbon complex is dissociated via the recombination-enhanced defect reaction.

Notes: Evidence is presented for strong correlation between new donors and rodlike defects generated at 650 °C in phosphorus-doped, carbon-lean Czochralski silicon preannealed at 450 °C. It is proposed that there are, in general, several types of new donors depending on experimental conditions, and one type of new donor, which is generated preferentially under the above special condition, arises from rodlike defects.

Notes: We have found with deep-level transient spectroscopy that chemical etching introduced three electron traps, E1(0.11), E2(0.13), and E3(0.15), in the near-surface region of phosphorus-doped crystalline silicon. The results on depth profiles of these traps and carriers suggested the donor character of the traps, but they hardly exhibited the Poole–Frenkel effect. From their correlations with carbon and oxygen, we propose a tentative identification that E1 and E2 traps arise from two kinds of hydrogen-oxygen-carbon complexes and the E3 trap arises from a hydrogen-carbon complex. Hydrogen is assumed to be adsorbed on the silicon surface during chemical etching and diffuse into the interior of the crystal during the subsequent evaporation and sample storage processes to be trapped at two kinds of oxygen-carbon complexes and substitutional carbon to form the traps. The annealing behavior of E2 and E3 traps in the dark were studied in detail. Their densities were increased at temperatures of 70–90 °C and subsequently were decreased at higher temperatures obeying first-order kinetics. The increase in trap densities is interpreted to be due to the further formation of the traps by capturing mobile hydrogen by oxygen-carbon complexes and substitutional carbon. This hydrogen is assumed to be released at temperatures of 70–90 °C by the dissociation of the hydrogen-phosphorus complex that was also formed by in-diffusing hydrogen during the evaporation and sample storage processes. The subsequent decrease in trap densities is attributed to the thermal dissociation of the traps at higher annealing temperatures and the subsequent loss of hydrogen at sinks. The illumination of band-gap light above 230 K annihilated the traps. The annihilation of the traps occurred only outside the depletion region of the Schottky structure. This effect is ascribed to the recombination-enhanced reaction, in which the electronic energy released by the electron-hole recombination at a trap level is converted into local vibrational energy to induce the thermal dissociation of the traps.

Notes: We have found by resistivity measurements and deep-level transient spectroscopy that four kinds of oxygen-related shallow donors, OD1–OD4, successively appear around 500 °C in the time region 10–106 min and carbon greatly affects their generation behavior in Czochralski silicon. The formation of OD2 and OD3 donors was enhanced by the presence of carbon, while that of OD1 and OD4 donors was retarded. The OD1 donor is identified as the so-called thermal donor that consists of several kinds of double donors observed so far by infrared studies. The OD2 donor is a new kind of donor discovered recently by us. OD3 and OD4 donors, which were formed by very prolonged annealing around 500 °C, are suggested to have correlations with so-called new donors normally generated above 600 °C. The origins of these oxygen-related donors are discussed in relation to oxygen precipitation.

Notes: We have found a hole trap related to hydrogen and carbon in p-type crystalline silicon after hydrogen and deuterium injection by chemical etching and plasma exposure. It was found from deep-level transient spectroscopy that this center is located at 0.33 eV above the valence band and shows no Poole–Frenkel effect in electric fields lower than 6×103 V/cm. The depth profiling technique using deep-level transient spectroscopy indicated that this center is distributed over the range 1–7 μm from the surface with densities of 1011–1013 cm−3, depending on the hydrogenation method. On the other hand, secondary ion mass spectroscopy revealed that the majority of deuterium injected into silicon exists within a much shallower region less than 60 nm from the surface with higher densities of 1018–1020 cm−3. We have therefore concluded that the majority of injected hydrogen stays in the near-surface region probably in the form of a molecule and larger clusters and only the minority diffuses into the bulk in an atomic form to form an electrically active complex with carbon. We performed annealing experiments to investigate the thermal stability of the complex. It was stable in the dark up to 100 °C, above which it was completely annihilated in first-order kinetics with an activation energy of about 1.7 eV. The illumination of band gap light with and without a reverse bias at room temperature and at 50 °C induced no effect on the stability of the trap. This is contrast to the photoinduced annihilation of a recently observed electron trap related also to hydrogen and carbon and with comparable thermal stability in n-type silicon.These similarities and differences between the two traps and the comparison of the present results with the recently published theoretical calculations of the total energy of hydrogen configurations in the hydrogen-carbon complex suggest that the previously observed electron trap and the presently observed hole trap arise from two different defects with similar origins and structures and are tentatively ascribed to the electronic states of "bond-centered'' and "anti-bonding of carbon'' configurations of hydrogen in the hydrogen-carbon complex, respectively. © 1995 American Institute of Physics.

Notes: It was found by secondary-ion mass spectrometry in-depth profiling technique that approximately 1×1020 iron atoms/cm3 accumulated at the Si-SiO2 interface of oxidized silicon crystals where iron was introduced by the indiffusion prior to the oxidation at 1000 °C and above. The origin of iron accumulation is ascribed to the iron precipitation from the bulk silicon. It was also found that iron atoms that diffuse in through the bulk from the lapped backside of a preoxidized sample were trapped and aggregated at the front Si-SiO2 interface. An interesting observation is shown that the above indiffusing iron also entered into the oxide region near the interface possibly to reduce SiO2.

Notes: The initial generation kinetics of thermal donors at 430 °C in Czochralski-grown silicon crystals containing (3–10)×1017 interstitial oxygen atoms per cm3 is studied by careful resistivity measurements at room temperature. The density of thermal donors is measured over the range from 1013 to 1016 cm−3. An analysis based on the chemical rate theory is made. For as-grown crystals, the well-known dependence of the initial donor formation rate and the maximum donor density on the initial oxygen concentration is confirmed. However, some irregularities are present in the very initial period of donor generation, probably arising from differences in thermal history of as-grown crystals. These irregularities are completely removed by pre-heating as-grown crystals at 1300 °C for 22 h and rapidly quenching them. In such heat-treated crystals, the initial kinetics of the thermal donor generation process can be described well by the following reaction scheme. The smallest donor species involving five oxygen atoms is preferentially formed, with its density being proportional to the square of the annealing time. Also, the electrically inactive cluster that involves four oxygen atoms and can be converted into the donor by the addition of an oxygen atom is simultaneously generated, while the formation and dissociation reactions for the smaller neutral clusters involving two and three oxygen atoms maintain the equilibrium. In as-grown crystals, the same reaction scheme can also explain the initial kinetics very well only if the initial densities of the smallest donor and the smaller neutral clusters are significantly increased, indicating that the initial irregularities are due to the differences in the densities of preexisting donors and neutral clusters.

Notes: We have discovered a new family of oxygen-related double donors [new thermal donors (NTD's)] generated around 450 °C in phosphorus-doped Czochralski silicon by combining deep-level transient spectroscopy with Hall measurements. This new family was well distinguished from the normal family of thermal donors (TD's) currently studied so far. Our results have shown that both families of thermal donors exhibit qualitatively the same kinetic behavior. Namely, as the annealing time increases, their ionization energy of levels continuously decrease with their densities increasing until the maxima and then become constant with their densities decreasing. However, there are significantly quantitative differences between the both families; NTD's have shallower levels, considerably smaller generation rates, and higher thermal stability than TD's. Sufficiently prolonged annealing for more than 105 min around 450 °C or short donor-killing annealing for 20 min at 650 °C completely annihilates TD's, leaving only NTD's, of which the most stable and therefore most shallow species have been suggested by our Hall measurements to have donor levels at 0.04 and 0.09 eV below the conduction-band edge. The density of interstitial oxygen still continues to decrease even after prolonged annealing for more than 105 min, where NTD's are present in a stable condition in a concentration of 1×1015 cm−3. NTD's may correlate with the NL10 electron paramagnetic resonance center because of similarities in their generation kinetics. We have suggested a hypothesis that NTD's have similar defect structures as TD's and that an unknown nucleus involved in the core of NTD's plays an essential role in lowering their ionization energy of levels and generation rates and also in stabilizing their donor activity.

Notes: We have evaluated hydrogen and deuterium diffusivities in silicon below room temperature (220–270 K) by analyzing the kinetics of photoinduced dissociation of a chemical etching introduced hydrogen (deuterium)–carbon complex. Under sufficiently strong illumination, the annihilation rate of the complex was proportional to the phosphorus density, indicating that the rate-determining step is the diffusion of hydrogen (deuterium) to phosphorus atoms. Applying the diffusion-controlled reaction theory, we have evaluated the diffusion coefficients as 7×10−2exp(−0.54 eV/kT) cm2 s−1 for hydrogen and 5×10−3exp(−0.49 eV/kT) cm2 s−1 for deuterium, being in good agreement with the extrapolation of the high-temperature diffusion data of A. Van Wieringen and N. Warmoltz [Physica 22, 849 (1956)].

Notes: We have found that at least four kinds of oxygen-related thermal donors are distinguishable by their deep-level transient spectroscopy peaks and generation kinetics around 520 °C for 10–106 min in phosphorus-doped Czochralski silicon. Each kind of thermal donors successively appeared with its preceding kind decaying. The first appearing kind is identified as a family of thermal donors that have been most studied by many investigators. It is suggested that several kinds of thermal donors arise from various oxygen clusters with different sizes and thermal stabilities.