Advanced hydrogenation process applied on Ge on Si quantum dots for enhanced light emission

Abstract

For the development of photonic integrated circuits, it is mandatory to implement light sources on a Si-on-insulator (SOI) platform. However, point defects in the Si matrix and, e.g., at the Si/SiO2 interface act as nonradiative recombination channels, drastically limiting the performance of Si-based light emitters. In this Letter, we study how these defects can be healed by applying an advanced hydrogenation process, recently developed in photovoltaic research for the passivation of performance-limiting defects in Si solar cells. Upon hydrogenation, we observe an increase in the room temperature photoluminescence (PL) yield by a factor of more than three for defect-enhanced quantum dots (DEQDs) grown on float-zone Si substrates, revealing the potential of this technique to passivate detrimental defects. For DEQDs grown using SOI substrates, the PL yield enhancement even exceeds a factor of four, which we attribute to the additional passivation of defects originating from the substrate. The results for SOI substrates are of particular interest due to their relevance for future photonic integrated circuits.

Photoluminescence enhancement by deterministically site-controlled, vertically stacked SiGe quantum dots

“…The samples were studied by micro-photoluminescence ( -PL) spectroscopy in a setup described in detail elsewhere 41 . For excitation a continuous-wave (cw) diode laser with a wavelength of 441 nm (532 nm frequency-doubled Nd:YAG laser for excitation-intensity-dependent measurements) was focused via a microscope objective with a numerical aperture of 0.7 onto a spot on the sample with a diameter of approximately 3 m and an adjustable excitation-intensity of up to 1100 kW cm .…”

“…Compared to a type-I heterosystem, the overlap of the wave functions is significantly reduced, and thus is the matrix element for radiative recombination 21 . A recent approach to address this problem utilizes deep-level Ge-ion-implantation into SiGe QDs, facilitating quasi-direct optical transitions 4 , 30 , 37 – 41 . This approach has been highly successful in achieving pronounced room-temperature light emission with further improvements achieved by annealing 42 and defect passivation in the surrounding Si matrix 40 , 41 .…”

“…A recent approach to address this problem utilizes deep-level Ge-ion-implantation into SiGe QDs, facilitating quasi-direct optical transitions 4 , 30 , 37 – 41 . This approach has been highly successful in achieving pronounced room-temperature light emission with further improvements achieved by annealing 42 and defect passivation in the surrounding Si matrix 40 , 41 . However, deep-level implantation has so far only been demonstrated with the hut-cluster-type 43 of SiGe QDs which have to be grown at temperatures too low to allow for efficient site-control 30 .…”

Photoluminescence enhancement by deterministically site-controlled, vertically stacked SiGe quantum dots

“…Compared to a type-I heterosystem, the overlap of the wave functions is significantly reduced, and thus is the matrix element for radiative recombination [21]. A recent approach to address this problem utilizes deep-level Ge-ion-implantation into SiGe QDs, facilitating quasi-direct optical transitions [4,30,[37][38][39][40][41]. This approach has been highly successful in achieving pronounced room-temperature light emission with further improvements achieved by annealing [42] and defect passivation in the surrounding Si matrix [40,41].…”

“…A recent approach to address this problem utilizes deep-level Ge-ion-implantation into SiGe QDs, facilitating quasi-direct optical transitions [4,30,[37][38][39][40][41]. This approach has been highly successful in achieving pronounced room-temperature light emission with further improvements achieved by annealing [42] and defect passivation in the surrounding Si matrix [40,41]. However, deep-level implantation has so far only been demonstrated with the hut-cluster-type [43] of SiGe QDs which have to be grown at temperatures too low to allow for efficient site-control [30].…”