This study explored the origin of the native donor in undoped In 2 O 3. The electronic structure of various point defects in In 2 O 3 clusters is studied using the first-principles molecular orbital calculation. The results show that an oxygen vacancy cannot act as a native donor, because the defect level formed is much lower than the bottom of the conduction band. However, interstitial indium can generate a shallow donor level, close to the conduction band, and an even shallower donor level is formed when it associates with an oxygen vacancy. It is concluded that the origin of the native donor in undoped In 2 O 3 is interstitial indium, but also that the existence of an oxygen vacancy is absolutely essential for carrier generation.

The crystal structures of methyl bromide and methyl iodide have been determined by the X-ray diffraction method at about −120°C and about −80°C respectively. Both the crystals are isomorphous, with orthorhombic space group D2h16–Pnma. Unit cells containing four molecules have the dimensions: a=4.474(1), b=6.420(2), and c=9.150(1) Å for methyl bromide, and: a=4.597(2), b=6.987(1), and c=10.117(1) Å for methyl iodide. These structures are quite different from that of methyl chloride, which has a symmetry of C2v12–Cmc21. In the three crystals, all the molecules are found on the mirror planes; the difference lies in the mutual orientations of the molecules.

The nitridation of silicon and oxidized‐silicon has been studied. The nitrided films were prepared at 900°–1150°C under ammonia partial pressures of 10−3 to 5 kg/cm2 in nitrogen and were analyzed by ellipsometry and Auger electron spectroscopy. For films formed by nitridation of silicon, we found that the growth kinetics and properties such as chemical composition, etching rate, and oxidation resistance were independent of the ammonia partial pressure. The nitridation of silicon can be explained by a modified Ritchie‐Hunt theory, which assumes that a very slow surface reaction at the ammonia‐nitride interface is the rate‐determining factor, using the logarithmic rate law. According to this modified Ritchie‐Hunt theory, the nitridation of silicon proceeds mainly by cation migration under a constant electric field. On the other hand, it was found that the nitridation of oxidized‐silicon depended strongly on the ammonia parital pressure. This dependence may be caused by diffusion of ammonia or its derivatives through the oxide. The conversion of silicon dioxide to silicon oxynitride occurred throughout the oxide.

We have studied the shrinkage and growth of preexisting oxidation-induced stacking faults during thermal nitridation of silicon without oxide film and of oxidized silicon with oxide film 23 to 5600 Å thick. Nitridation was carried out at 1050 to 1200 °C under ammonia partial pressures of 10−3 to 4 kg/cm2. We observed that stacking faults in silicon without oxide film shrink linearly with nitridation time and their shrinkage rate increased as the partial pressure of ammonia increased. On the other hand, stacking faults in oxidized silicon with oxide film grew during nitridation and their growth rate increased with the increase of ammonia partial pressure after the pressure reached about 10−1 kg/cm2 and with the increase of the thickness of the oxide film. Based on these results, we have proposed a model which assumes that in the shrinkage phenomenon, an undersaturation of silicon self-interstitials occurs near the silicon surface because of silicon-cation migration from the silicon-nitride interface to the nitride surface. The model also assumes that the growth phenomenon occurs because of the supersaturation of silicon self-interstitials, which are generated by the reaction of ammonia with silicon dioxide and are injected into the bulk of silicon through the silicon-nitride interface. The projected results of this model agree reasonably well with the experimental results.

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Lattice defects induced by laser irradiation and their thermal stability during subsequent oxidation were studied by transmission electron microscopy, x‐ray topography, and preferential etching. High power laser pulses above 20 J/cm2 produced dislocation lines and dislocation clusters. Laser pulses of about 15 J/cm2 also generated dislocation clusters and pseudo‐swirl defects in the irradiated region. All of these defects were thermally stable. However, thermally stable defects were not observed when laser pulses of less than 15 J/cm2 were used, although unstable dislocations were generated. The suppression of defect formation by laser damage gettering was examined using Sirtl etching. It was found that thermally stable dislocations and pseudo‐swirl defects acted as sinks for point defects and prevented the formation of precipitates during a subsequent oxidation. Laser damage gettering was used to improve generation lifetime in metal‐oxide‐semiconductor (MOS) capacitors with the result that generation lifetime in the gettered area was improved by two orders of magnitude over that in the ungettered area.

We have studied the change in morphology of laser irradiated silicon wafers by annihilating the oxygen thermal donors and the oxidation-induced stacking faults in order to verify the melting of the near-surface regions. The laser beam used was of 1.06 μm with a diameter of 40 μm, generated from a Q-switched neodymium:yttrium aluminum garnet (Nd:YAG) laser with a 150-ns pulse width and at a repetition rate of 12 kHz. Laser beam irradiation above about 6 J/cm2 annihilated both thermal donors and stacking faults, giving evidence of melting and suggesting that the annihilation of the thermal donors and of the stacking faults can be useful in studying the surface morphology in laser/electron beam irradiation.

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