Interplay of strain and intermixing effects on direct-bandgap optical transition in strained Ge-on-Si under thermal annealing

Abstract

The influence of thermal annealing on the properties of germanium grown on silicon (Ge-on-Si) has been investigated. Depth dependencies of strain and photoluminescence (PL) were compared for as-grown and annealed Ge-on-Si samples to investigate how intermixing affects the optical properties of Ge-on-Si. The tensile strain on thermally annealed Ge-on-Si increases at the deeper region, while the PL wavelength becomes shorter. This unexpected blue-shift is attributed to Si interdiffusion at the interface, which is confirmed by energy dispersive X-ray spectroscopy and micro-Raman experiments. Not only Γ- and L-valley emissions but also Δ 2 -valley related emission could be found from the PL spectra, showing a possibility of carrier escape from Γ valley. Temperature-dependent PL analysis reveals that the thermal activation energy of Γ-valley emission increases at the proximity of the Ge/Si interface. By comparing the PL peak energies and their activation energies, both SiGe intermixing and shallow defect levels are found to be responsible for the activation energy increase and consequent efficiency reduction at the Ge/Si interface. These results provide an in-depth understanding of the influence of strain and Si intermixing on the direct-bandgap optical transition in thermally annealed Ge-on-Si.

GaN MSM structure UV photodetector detector based on nonplanar Si substrate and its performance optimization

“…Furthermore, it should be noted that a blue shift of ∼1.4 cm −1 occurred for GaN/Si-NPA after annealing treatment, which reflects a stress release over 258.4 MPa. According to the experiments conducted by other groups [30], this phenomenon should be attributed to the interdiffusion of Si and GaN at the interface under high temperature annealing, which surely causes the reduction of residual stress. The results show that the film residual stress can be largely reduced by using patterned Si-NPA substrate, which might be very helpful for improving the quality of GaN films effectively.…”

Towards white light laser emission based on strained Poly:(Si/Ge)

“…This can be explained as mentioned before: In the heterostructure on FTO, the diffusion rate of metals in Ge is higher since the surface area of interaction between Ge and metal layers increases as a result of the change in morphology of the FTO bottom layer as a result of the high annealing temperature near its melting point. In the case of heterostructure on p-Si, the Al atoms doesn't segregate in the p-doped substrate but these atoms of Al layer are rapidly segregating in the lower majority carriers concentration intrinsic Ge layer and thus increase the rate of crystallization and incorporation of Sn increasing GeSn direct allowed transition [27]. A direct transition of GeO for all heterostructures is ranged between 1.15 to 1.85 eV due to different level of oxygen incorporation in the samples [27].…”

“…In the case of heterostructure on p-Si, the Al atoms doesn't segregate in the p-doped substrate but these atoms of Al layer are rapidly segregating in the lower majority carriers concentration intrinsic Ge layer and thus increase the rate of crystallization and incorporation of Sn increasing GeSn direct allowed transition [27]. A direct transition of GeO for all heterostructures is ranged between 1.15 to 1.85 eV due to different level of oxygen incorporation in the samples [27]. Another direct transition at Ge crystallites of higher level of oxidation is around 2.02 up to 2.73 eV occurs in the structures prepared on FTO and p-Si substrates.…”

First-principles prediction of electronic transport in fabricated semiconductor heterostructures via physics-aware machine learning

“…Silicon (Si)/germanium (Ge) heterostructures, in particular, have emerged as key materials in numerous electronic [2][3][4][5] , optoelectronic 6,7 and thermoelectric devices 8,9 , and promising hosts of spin qubits 10 . Recent developments of nanofabrication and characterization techniques achieved great control over the growth of Si/Ge heterostructures [11][12][13][14][15] . Nevertheless, fabrication of heterostructures is strongly affected by strain relaxation in component layers 5 , and the resulting electronic properties show high variability due to fabrication-dependent structural parameters 9,16,17 .…”