Direct-Gap Gain and Optical Absorption in Germanium Correlated to the Density of Photoexcited Carriers, Doping, and Strain
Abstract
Direct-gap gain up to 850cm-1 at 0.74 eV is measured and modeled in optically pumped Ge-on-Si layers for photoexcited carrier densities of 2.0×1020cm-3. The gain spectra are correlated to carrier density via plasma-frequency determinations from reflection spectra. Despite significant gain, optical amplification cannot take place, because the carriers also generate pump-induced absorption of ≈7000cm-1. Parallel studies of III-V direct-gap InGaAs layers validate our spectroscopy and modeling. Our self-consistent results contradict current explanations of lasing in Ge-on-Si cavities.
- Publication:
-
Physical Review Letters
- Pub Date:
- August 2012
- DOI:
- 10.1103/PhysRevLett.109.057402
- Bibcode:
- 2012PhRvL.109e7402C
- Keywords:
-
- 78.66.Db;
- 42.55.Px;
- 42.72.Ai;
- 78.66.Fd;
- Elemental semiconductors and insulators;
- Semiconductor lasers;
- laser diodes;
- Infrared sources;
- III-V semiconductors