Yu Murao

Impurity effects on the generation and velocity of dislocations in Ge

The dynamic behavior of dislocations in heavily impurity (Ga, As, O) -doped Ge crystals was investigated as a function of stress and temperature by means of the etch-pit technique. The Ga and O impurities effectively suppressed dislocation generation from a surface scratch, while the As impurity did not strongly do so. Dislocations in Ga- and O-doped Ge crystals were supposed to be immobilized by the stable complexes formed through the impurity segregation and reaction. Remarkably, the O impurity, even at a low concentration of 1016 cm−3, induced the suppression of dislocation generation. The As impurity enhanced and the Ga impurity retarded dislocation velocity in motion. The O impurity had no effect on the velocity of the dislocations.

Behaviour of oxygen-related thermal donors in Ge crystals Czochralski-grown from the melt covered fully by B2O3

Oxygen-related thermal donors (OTDs) in oxygen-enriched Czochralski Ge crystals grown from a melt fully covered by B2O3 liquid were investigated by infrared spectroscopy. Interstitially dissolved oxygen concentrations [Oi] and thermal donor concentrations NTD in Ge specimens annealed at 350°C for 64h and at 550°C for 1h, followed by subsequent fast cooling to room temperature, were measured in comparison with those in as-grown Ge. By annealing at 350°C, an absorption peak developed at 780 cm−1 and the peak height at 855 cm−1 related to [Oi], decreased. The absorption coefficient at 780 cm−1 showed the same correlation to the difference between the total concentration of oxygen atoms and the dissolved oxygen concentration in the annealed specimens. It was found that the number of oxygen atoms forming the OTD increases with increasing annealing time at 350°C.

Interstitial oxygen behavior for thermal double donor formation in germanium: Infrared absorption studies

The kinetics of the reduction of interstitial oxygen (Oi) due to the formation of thermal double donors (TDDs) upon heat treatment in an oxygen-rich Ge crystal were investigated at various temperatures. Specimens were prepared from a Ge crystal with oxygen at a concentration of 4–5 × 1017 cm−3 grown by a new Czochralski method and were heat-treated in the temperature range 300–500 °C. Shrinkage of a dissolved oxygen absorption peak at 855 cm−1 and simultaneous development of a thermal double donor peak at 780 cm−1 were observed by infrared absorption spectroscopy at room temperature. The formation of TDDs was also detected electrically. Reduction of dissolved oxygen concentration upon the heat treatments was kinetically analyzed. The activation energy of the reduction of Oi concentration was evaluated to be 1.7 and 2.0 eV in the early and prolonged stages of the heat treatment, respectively, close to that of Oi diffusion. From the results, TDD development process was indicated to be the merge reaction of ...

Formation of Thermal Double Donors in Ge

Formation of thermal double donors (TDDs) by aggregation of interstitially dissolved oxygen (Oi) was investigated for an oxygen-enriched Ge in an annealing at 300-500°C by infrared absorption spectroscopy. The formation of TDDs was supposed to be two reactions: In the primary stage of annealing, the merge reaction of two Ois is dominant to form an oxygen-dimer as a TDD nucleus. In the secondary stage, TDDs grow larger by absorbing an Oi is dominant. At higher temperatures dissociation of TDDs should be included. In the thermal equilibrium state at 325-400°C TDD involves 16-19 Oi in average.