Electroluminescence from strained SiGe quantum dot light-emitting diodes

Abstract

In order to overcome the speed limitation of electrical interconnects, we integrate ultra large scale integrated (ULSI) circuits with the electro-optics. Besides the modulator, both the light emitting diode (LED) and the detector are essential to achieve this goal. In order to get greater functionality, we integrate Si chip with the Si based electro-optics. For the time being, the light emitter is the key point of the electro-optics based on Si. In this work, the metal-oxide-semiconductor tunneling diode is used to emit electroluminescence. Raman spectroscopy reveals that the expected pure Germanium (Ge) quantum dot (QD) grown by ultra high vacuum chemical vapor deposition (UHVCVD) at 625degC exhibits significant intermixing with the average Ge composition of ~ 56%. It also shows that the top SiGe quantum dot of the 20-layer QD sample (66% relaxation) have more relaxation than the 5-layer QD sample (58% relaxation). The photoluminescence (PL) emission peak intensity from the 20-layer QD is increasing with the temperature decreasing. Besides the 1.1 mum infrared from the band edge of Si, the 1.5 mum infrared emission due to the radiative recombination between the electrons in the Si conduction band and the holes in the SiGe valence band is also observed. The emission line shape can be fitted by the electron-hole-plasma recombination model. The electroluminescence from the top SiGe quantum dot shows that the 20-layer QD sample (0.76% compressive strain) has the higher emission peak energy at ~0.84 eV as compared with the 5-layer QD sample (0.93% compressive strain) with the emission peak energy at ~0.82 eV.