Münster 1997 – scientific programme

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HL: Halbleiterphysik

HL 19: Si/Ge II

HL 19.5: Talk

Tuesday, March 18, 1997, 17:00–17:15, H2

Light Emission from Si-Si_1−xGe_x Quantum Dots with Different Internal Strain — •C.M. Sotomayor Torres³, Y.S. Tang¹, S.E. Hicks¹, W.-X. Ni², C.D.W. Wilkinson¹, and G.V. Hansson² — ¹Nanoelectronics Research Centre, University of Glasgow, UK — ²Department of Physics, Linköping University, Sweden — ³Institut für Materialwissenschaften, Universität Wuppertal, 42097 Wuppertal

Based on the enhanced optical emission observed from 50 nm Si-Si_1−xGe_x quantum dots, we have realised efficient light emitting diodes by using polyimide as the planarization layer. However, polyimide results in unstable I-V curves. The use of normal Si₃N₄ for planarization reduces light emission efficiency due to the extra-stress in the dots. We report our recent results on light emission from a series of Si-Si_1−xGe_x quantum dots coated with a novel a-SiN_x layer with controlled built-in stress. When the external stress around the dots is changed from compressive to tensile, the weak two-peak-spectrum (no-phonon and TO phonon assisted transitions) evolves into one intense peak at around zero stress, and then changes back into two weak peaks. The corresponding emission energy shifts from 1.041eV to 1.032eV at 6K. These results suggest that strain and lattice distortion play key roles in the observed enhanced light emission phenomenon.