Infrared emission from Ge metal-insulator-semiconductor tunneling diodes

The Ge light-emitting diode with similar to 1.8 mu m strong infrared emission is demonstrated using a metal-insulator-semiconductor tunneling structure. The intensity of a Ge device is one order of magnitude stronger than a similar Si device. At the positive gate bias, the holes in the Al gate electrode tunnel to the n-type Ge through the ultrathin oxide and recombine radiatively with electrons. An electron-hole-plasma model can be used to fit all the emission spectra from room temperature down to 65 K. From the measurement temperature range, the extracted band gap is similar to 40 meV lower than the reported band gap data, and the linewidth drops from 70 to 25 meV. The longitudinal acoustic phonon (similar to 28 meV) and/or the band gap renormalization at high carrier density are proposed to be responsible for the reduction of photon energy. The band gap reduction on the mechanically strained n-type Ge and Si is also investigated experimentally and theoretically. (c) 2006 American Institute of Physics.