Infrared emission from Ge metal-insulator-semiconductor tunneling diodes

Abstract

The Ge light-emitting diode with ∼1.8μm 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 65K. From the measurement temperature range, the extracted band gap is ∼40meV lower than the reported band gap data, and the linewidth drops from 70to25meV. The longitudinal acoustic phonon (∼28meV) 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.