According to Taiwan media reports, the silicon microelectronics industry is the most commonly used material, but because of its indirect energy band (indirect bandgap), luminous efficiency is very low. Recently, the National Taiwan University Department of Materials Science and Engineering, and Professor Yang Zheren Professor Chen Minzhang led research team, using n-type zinc oxide / silicon dioxide - silicon nano ceramic - silica / p-type Si substrate (n- ZnO/SiO2-Si nanocrystal-SiO2/p-Si) of the heterostructure, successfully produce high-efficiency silicon light-emitting diodes, non-direct band semiconductor in optoelectronic applications on the new opportunities opened up.
NTU team first by low pressure chemical vapor deposition (LPCVD) growth in the p-type silicon of silicon nano-ceramic plate, and then thermal oxidation (thermal oxidation) the ceramic layer embedded in silicon dioxide. Followed by atomic layer deposition technique (Atomic Layer Deposition, ALD) production of high-quality n-type ZnO films as transparent conductive layer, electron injection layer and can improve the light extraction efficiency of the anti-reflective layer. ALD thin film deposition for advanced nano technology to form an atomic-level precision control of film thickness and composition, also has high uniformity and low defect density, large area production batches, and the advantages of sedimentary and low temperature .
Electron microscopy pictures clearly show a diameter of about 24 nm of silicon nano-crystallite embedded in the thickness of about 9.2 nm of silicon dioxide layer. Electron and hole respectively n-type ZnO films with p-type Si substrate, tunneling (tunneling) through the silicon dioxide layer into the silicon nano-crystallite. Because of electron hole pairs are confined in a small ceramic, the silicon dioxide on the role of ceramic surface defect repair again, so light generated electron hole pairs with (radiative recombination) greatly increased the probability, combined with transparent ZnO thin films The anti-reflective effect, and thus greatly enhance the efficiency of silicon light emitting diodes.
The components of the room Wen Faguang spectrum peak at the wavelength of 1140 nm, very close to the silicon energy band gap, corresponding to the phonon assisted carrier with non-direct (phonon-assisted indirect carrier recombination) the physical mechanism. The researchers also measured the DC current into the light of different power. This component at room temperature external quantum efficiency as high as 4.3 × 10-4, is when the bulk silicon substrate 100 times, speculation about the internal quantum efficiency of 10-3, breaking an indirect band semiconductor restrictions.
It is worth mentioning that this component of process and structure with the current VLSI technology is completely compatible, can be directly integrated circuits which in the present. Results of this study is expected to optical integrated circuits used in connection (optical interconnection), and optical
