Defect-free Ge-on-insulator with (100), (110), and (111) orientations by growth-direction-selected rapid-melting growth

Defect-free Ge-on-insulator (GOI) with various crystal orientations is essential to realize high-speed and multifunctional devices. Seeded rapid-melting growth of GOI is investigated as a function of seed-orientations and growth-directions. From (100)-oriented Si seeds, Ge growth with a (100) orientation propagates for all growth-directions, however, rotational-growth is observed for some directions when Si seeds with (110) and (111) orientations are used. Such rotational-growth can be completely suppressed by selecting the growth-directions deviating from (111) by more than 35°. Transmission-electron-microscopy observation shows no-stacking fault and no-dislocations. Consequently, defect-free GOI with (100), (110), and (111) orientation is achieved, which demonstrates high-hole mobility (~1100 cm²/V s).