Verifying the band gap narrowing in tensile strained Ge nanowires by electrical means

Abstract

Group-IV based light sources are one of the missing links towards fully CMOS compatible photonic circuits. Combining both silicon process compatibility and a pseudo-direct band gap, germanium is one of the most viable candidates. To overcome the limitation of the indirect band gap and turning germanium in an efficient light emitting material, the application of strain has been proven as a promising approach. So far the experimental verification of strain induced bandgap modifications were based on optical measurements and restricted to moderate strain levels. In this work, we demonstrate a methodology enabling to apply tunable tensile strain to intrinsic germanium 111 nanowires and simultaneously perform in situ optical as well as electrical characterization. Combining I/V measurements and μ-Raman spectroscopy at various strain levels, we determined a decrease of the resistivity by almost three orders of magnitude for strain levels of ∼5%. Thereof, we calculated the strain induced band gap narrowing in remarkable accordance to recently published simulation results for moderate strain levels up to 3.6%. Deviations for ultrahigh strain values are discussed with respect to surface reconfiguration and reduced charge carrier scattering time.

In situ x-ray analysis of misfit strain and curvature of bent polytypic GaAs–In x Ga1−x As core–shell nanowires

“…straight. The realization of a spatially varying strain field can be induced by bending the nanowire which opens up new possibilities for strain and band-gap engineering [10][11][12][13][14]. Spontaneous nanowire bending can be achieved by an asymmetric shell growth around a lattice mismatched nanowire core [10,15,16].…”

Enhancing Short-Wave Infrared Photosensitivity of SiGe Nanocrystals-Based Films through Embedding Matrix-Induced Passivation, Stress, and Nanocrystallization

“…46 The contribution of strained Ge-rich SiGe NCs (0.6% strain) was evidenced in the photocurrent spectra by the high sensitivity in SWIR up to 2000 nm at 100 K (1800 nm at 300 K) (Figure 12). 47 Tensile strain drastically reduces the bandgap (compared to strain-free SiGe NCs) 89 while the high quality SiGe NC/ nanocrystallized HfO 2 matrix interface (i.e., effective SiGe NC surface passivation) ensures the high sensitivity as the NC surface/interface is free of defects. So, in this case, strain in NCs together with good NC surface passivation lead to enhanced SWIR photosensitivity with a SWIR extended cut-off wavelength deeper than expected for bulk Ge-rich SiGe and Ge.…”

Exploiting flux shadowing for strain and bending engineering in core–shell nanowires

“…Due to their large surface to volume ratio, NWs have sizedependent mechanical properties allowing for strain engineering [1][2][3] . Strain engineering can be used to tune the electronic band gap and to tailor the performance of NW-based devices [4][5][6] . Additionally, piezoelectric fields in strained NWs can be utilized for efficient carrier sweeping toward device electrodes [7][8][9] .…”

“…[1][2][3] Strain engineering can be used to tune the electronic band gap and to tailor the performance of NWbased devices. [4][5][6] Additionally, piezoelectric fields in strained NWs can be used for efficient carrier sweeping toward device electrodes. [7][8][9] Therefore, strained heteroepitaxial core-shell NWs formed from lattice-mismatched materials have potential applications in NW-based devices such as light-emitting diodes, 10,11 solar cells, [12][13][14][15] and electronic devices.…”