An infrared transmission study of Ge:Mn thick films prepared by ion implantation and post-annealing

Ge:Mn thick films ( t ≈ 3  μm) with low average Mn concentration ( < 0.3%) were prepared by ion implantation at 77 K followed by either conventional or flashlamp annealing. The films were characterized by x-ray diffraction, secondary ion mass spectrometry, magnetometry, and infrared transmission (100–6500 cm − 1). Post-annealing at a high enough temperature recrystallizes the amorphous Ge:Mn films without significant migration of Mn to the surface, while solid phase epitaxy does not occur, resulting in polycrystalline films. Annealing causes an estimated 50%–80% of the implanted Mn to migrate to Mn-rich clusters or form Mn 5Ge 3, while the remainder enters the Ge lattice substitutionally creating free holes. Evidence for free holes comes from the structure in the mid-infrared absorption coefficient that is similar to previous observations in p-type Ge. The data suggest that the maximum solubility of Mn in the Ge crystalline lattice has an upper limit of < 0.08%.