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The optical microscope image of Ge-on-Si after Secco etching. The threading dislocation density is . The defects are marked with circles. The inset is the TEM image of Ge-on-Si.
The PL spectra of the bulk Ge and Ge-on-Si at room temperature. The integrated PL intensity ratios of the direct to indirect band gap transition of the bulk n-Ge and Ge-on-Si sample are 0.05 and 2.5, respectively. The bulk Ge is times the integrated intensity of PL of the Ge-on-Si sample.
The schematic band diagram of the Ge (a) without defects and (b) with defects. The large defect density leads to trap levels broadened in momentum space.
The EL spectra of the Ge and Ge MIS LEDs at an injection current of 300 mA at room temperature. The roughness scattering conserves the momentum and increases the indirect radiative transition. The inset is the schematic band diagram of the light emission process of the MIS LED.
The PL and EL spectra of MIS LED at room temperature. There is no direct band transition observed in the EL spectra.
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