High-efficiency silicon-compatible photodetectors based on Ge quantum dots

Abstract

We report on high responsivity, broadband metal/insulator/semiconductor photodetectors with amorphous Ge quantum dots (a-Ge QDs) as the active absorbers embedded in a silicon dioxide matrix. Spectral responsivities between 1-4 A/W are achieved in the 500-900 nm wavelength range with internal quantum efficiencies (IQEs) as high as ∼700%. We investigate the role of a-Ge QDs in the photocurrent generation and explain the high IQE as a result of transport mechanisms via photoexcited QDs. These results suggest that a-Ge QDs are promising for high-performance integrated optoelectronic devices that are fully compatible with silicon technology in terms of fabrication and thermal budget. © 2011 American Institute of Physics

Light harvesting with Ge quantum dots embedded in SiO2 or Si3N4

“…This can be due to the high potential barrier and to the larger film thickness offered by the SiGeO samples. For this reason, in the following, we present our best results obtained with the SiGeN samples containing 1.5 nm sized Ge QDs with a density of 6.5 Â 10 19 QD/cm 3 . As shown in Figure 7(a), upon illumination with white light the current density in forward bias remains largely unaffected, while it increases more than one order of magnitude in reverse bias.…”

“…The proposed mechanism has been successfully used for modeling photo-detection in layers of Ge QDs in SiO 2 synthesized by magnetron sputtering. 3 In that case, substrate was n-type doped and device responsivity was larger. 3 Even if the substrate doping changes or the QD embedding matrix is different, a clear role of Ge QDs as trapping centers for one species of charge carriers comes out.…”

“…3 In that case, substrate was n-type doped and device responsivity was larger. 3 Even if the substrate doping changes or the QD embedding matrix is different, a clear role of Ge QDs as trapping centers for one species of charge carriers comes out. Finally, it should be noted that, for PECVD materials reported in this paper, only QDs in Si 3 N 4 display a marked photo-detection behavior, as QDs in SiO 2 grown by PECVD do not reveal significant activity under illumination.…”

“…In the past decade, group-IV nanostructures (NS) received much attention as new material for efficient optoelectronic devices, 1,2 photodetectors, 3,4 and solar cells. 5,6 In particular, Ge nanostructures gained a renewed interest because of their larger absorption, stronger quantum confinement effect (QCE) due to the larger Bohr radius ($24 nm) 7,8 and lower synthesis temperature in comparison with Si nanostructures.…”

“…The exploitation of these properties and their application for efficient light harvesting devices have been quite extensively studied in recent years. Ge quantum dots (QDs) in SiO 2 have been already used for the fabrication of QD-based memories, 9 efficient light harvesters, 2,3,10 or for the application in novel multi-junction solar cells. 6,11 However, the optical behavior and the band-gap tuning of Ge QDs does not depend on QD size only, as a basic confinement effect rule predicts.…”