Enhanced photoluminescence of heavily n-doped germanium

We show that a significant enhancement of the direct band gap photoluminescence can be achieved at room temperature in bulk Ge and Ge-on-insulator heavily n-doped by gas immersion laser doping. The photoluminescence signal from bulk Ge and Ge-on-insulator increases with the donor concentration. An enhancement factor of 20 as compared to the undoped material is achieved near the 1550 nm wavelength for active dopant concentrations around 5x10(19) cm(-3). These results are supported by calculations of the Ge spontaneous emission spectrum taking into account the doping effect on the electron distribution in the direct and indirect conduction band valleys.