Infrared and Photoluminescence Spectroscopy of p-doped Self-Assembled Ge Dots on Si

We report photocurrent (PC) and photoluminescence (PL) spectroscopy of self-assembled Ge dots grown on Si(100) by molecular beam epitaxy. PL spectra show a transition from two-dimensional to three-dimensional growth as the Ge thickness exeeds 7angstroms. The sum of the PC peak energy and PL energy from Ge dots is found to be approximately equal to the energy band gap of Si. Boron doping changes the energy spectrum of the dots: PL peaks from both doped Ge dots and from the wetting layer and shifted to higher energy, compared to the undoped samples. Also, the TO phonon energy from the wetting layer is reduced to 38 meV.