Luminescence in selectively excited germanium microcrystallites

We have obtained the luminescence spectrum from Ge microcrystallites selectively excited. The spectrum has a broad feature with several structures, which are classified into two categories: a steplike structure near the excitation energy with an onset energy of 23 meV that is assigned to the phonon structure due to the LA$(L)$ phonon, and a feature with three peaks at larger energy shifts (220, 380, and 590 meV) from the excitation energy. The results suggested a close similarity of the luminescence mechanisms of the Ge microcrystallite system and porous Si.