Physical basis and characteristics of light emission from quantized planar Ge structures

The characteristics of luminescence from quantized planar Ge structures are presented, showing stability with time, dependence on laser power excitation and temperature, and the presence of GaAs-Al/sub 0.8/Ga/sub 0.2/As overlayers. A single broad emission at 1.7 eV near 300 K is observed to become four distinct emissions at 2.16 eV, 2.01 eV, 1.696 eV, and 1.56 eV at 77 K. A model describing the basis of luminescence in small Ge structures is also presented. The increased probability for radiative recombination in the quantized structures is a result of states in the conduction band and valence band being closed in k-space than in bulk Ge. Thus, the luminescence at 1.7 eV in the quantized structures probably results from a one or two phonon-assisted process compared to a 4-5 phonon process in bulk Ge for photoluminescence at 0.7 eV.<>