2, Novosibirsk State University, Novosibirsk, , Russian Federation
3, Tomsk State University, Tomsk, , Russian Federation
4, CEA, LETI, Minatec Campus and Université Grenoble Alpes, Grenoble, , France
The major challenges for semiconductor fundamental research and technological development are confined to a variety of silicon-based nanostructured systems. The present talk aimed to show results and technology development in Si/Ge quantum dots (QDs) heterostructures, grown by molecular beam epitaxy. Hole transitions between the ground state confined in Ge dots to valence band continuum are fit to middle infrared (IR) range 3 - 5 μm. The disadvantage of SiGe-based QDIPs is the low absorption coefficient and hence small photoresponse in the mid-wavelength IR region. We have developed a few approaches allowing to improve performances of SiGe-based QDIPs. 1) A remarkable property of QDs originated from their discrete energy spectrum is a suppression of carrier relaxation rates due to the phonon bottleneck effect. In Ge/Si(001) QDs heterostructures we observed the general tendency: with decreasing the size of the dots, the dark current and hole capture probability are reduced, while the photoconductive gain and photoresponse are enhanced. It is attributed to a quenched electron-phonon scattering due to phonon bottleneck [Appl. Phys. Lett.,107, 213502 (2015)]. 2) The studies of the effect of quantum dot charging on the mid-infrared Ge/Si QDIPs operation have shown that doping to contain from about one to nine holes per dot induce an over 10 times gain enhancement and similar suppression of the hole capture probability with increased carrier population. The data are explained by quenching the capture process due to formation of the repulsive Coulomb potential of the extra holes inside the quantum dots [Mater. Res. Express 3, 105032 (2016)]. 3) The plasmonic sensing of Ge/Si QDIPs with wavelength optical response and polarization selectivity was found to show the most pronounced phenomenon. Ge/Si QDs heterostructures were monolithically integrated with periodic two-dimensional arrays of subwavelength holes perforated in gold films to convert the incident electromagnetic IR radiation into the surface plasmon polariton waves. The resonant responsivity of the plasmonic detector at a wavelength of 5.4 μm shows an enhancement of up to thirty times over a narrow spectral bandwidth (FWHM 0.3 um), demonstrating the potentiality of this approach for the realization of high-performance Ge/Si QDIPs [J. Appl. Phys., 122, 133101 (2017)]. 4) The growth of Ge/SiGe QDIPs on a virtual Si(1-x)Gex (x=0.18) substrate show an over 100% photovoltaic response enhancement as compared to a conventional Ge/Si device due to smaller hole effective mass in the SiGe layers. A further enhancement in sensitivity is achieved by photodetector coupled with a plasmonic structure. The responsivity and detectivity values for the detector are 40 mA/W and 1,4 x 1011 cm Hz1/2/W at 90 K for zero bias operation, which are comparable or higher than n-type InAs/GaAs QDIPs [Optics Express, 25, No. 21, 16 Oct 2017]. The work was funded by Russian Scientific Foundation (grant 14-12-00931 Π).