We studied the photoreflectance (PR) and photoluminescence (PL) spectroscopies of self-assembled InAs quantum dots grown on n+-GaAs (100) by molecular beam epitaxy. The PL spectroscopy of self-assembled Ge quantum dots (Ge-QDs) grown on n+-Si (100) by metal organic chemical vapor deposition epitaxy was also investigated. PL spectra show the optical transitions from the ground state and excited states in the InAs quantum dots (InAs-QDs) and a transition from the ground state in the Ge-QDs at the temperature 20 K. PR spectra show the energy features of the transitions of the ground state and four excited states in the InAs-QDs, InAs wetting layer, and GaAs band-gap. The fitted results of the transition energies and the broadening parameters are reported. The results demonstrate that low growth rate of the InAs-QDs, the submonolayer deposited of the alternating beam, and covered with the overgrowth InGaAs methods, have improved the nano-structure quality of the InAs-QD, grown at 485ºC and V/III ratio of 2. The high quality Ge-QDs were made, and characterized by PL experiments.