Low-temperature crystallization of Ge-rich GeSn layers on Si3N4 substrate

Solid phase crystallization (SPC) of amorphous GeSn (a-GeSn) layers with a Sn content of 2% on various insulating substrates of Si3N4, sapphire, and Y2O3 have been investigated. We found that Si3N4, which has almost same value of a higher surface energy with sapphire and the value is about twice as high as Y2O3, could be reduced the SPC temperature of a-GeSn layers (to 400 °C) compared with the other cases. We can see that a maximum grain size as large as 0.9 µm was achieved for polycrystalline GeSn layers on Si3N4 by the annealing at 450 °C for 5 h. Correspondingly, a relatively higher Hall hole mobility (180 cm2/Vs) was obtained.