Oxygen loss and thermal double donor formation in germanium

Kinetics of interstitial oxygen loss and oxygen-related thermal double donor (TDD) generation upon heat treatments of Ge:O crystals at 350 °C have been studied. The TDD concentration (NTDD) was derived from Hall effect measurements in the temperature range 77–400 K. The bistability of the first TDD species was taken into account. The interstitial oxygen concentration ([Oi]) in the crystals was determined from measurements of the intensity of the infrared absorption band at 855 cm−1 at room temperature with the use of a recently obtained calibration coefficient CO=1.05×1017 cm−2. From an analysis of the [Oi](t) and NTDD(t) kinetics a confirmation of recent suggestions about faster diffusivity of small oxygen clusters compared to the diffusivity of single interstitial oxygen atoms was obtained. Average numbers (N) of oxygen atoms lost per TDD species created, N=Δ[Oi]/NTDD, were calculated at different stages of the TDD generation. The obtained values of N are consistent with those expected in accordance with the recent models of the TDD structure. In particular, an average number of oxygen atoms per TDD species was about 5 at initial stages of the heat treatment when the first members (the TDD2 and TDD3 species) of the TDD family were dominant. N was found to be about 10 after extended anneals at 350 °C when the TDD6 and TDD7 species were dominant.