Metal-semiconductor Contact Of Black Silicon And Its Electrical Properties

The crystalline silicon is well known as a semiconductor with an indirect band gapand a large band gap. So, it can only absorb the visible light effectively. Throughmicro-etching and elements doping onto the surface of crystalline silicon wafer, anetched surface microstructure can be obtained, which has excellent light trapping abilityand wider spectral response. This new textured surface structure is called black silicon（BS）. Compared with the conventional Si-based photo-detectors, the detectors based onblack silicon have the ability to detect the infrared light, and can broaden the responsespectrum of incident beam. In recent years, by virtue of so many excellent optical andelectrical characteristics, black silicon has become one of the most importantsilicon-based photoelectric materials, and it has also been used widely in thephotoelectric detection of visible-near infrared beam and also in the field of efficientthin film solar cells.Any electronic devices based on semiconductor materials must have a goodelectrical contact between the metal electrodes and the semiconductor materials. Basedon the requirement of the scientific study and the device application, the investigationon the metal-black silicon contact was carried out systematically in this thesis. The maincontents of the research include:1)The samples of black silicon with different depth of holes are prepared by thesingle-slot electrochemical methods.2)Different kinds of metals are deposited into the surface of black silicon whichhas many holes of3¹0μm in depth by different ways, including thermal evaporation,magnetron sputtering and electroless deposition （the traditional electroless depositionand the direct electroless deposition）.3)The micro-topographic images of different interface, including Al/BS, Ni/BS,NiCr/BS and NiP/BS, are observed by scanning electron microscopy （SEM）. Thecontacting behavior of metal to black silicon is tested and analyzed in the models oflongitudinal I-V test and dot-type transmission line, respectively.The results indicate that①due to the shadow effect, Al and Ni that were deposited by thermal evaporation can’t fill the holes of black silicon completely.②theNiCr plating that was coated by sputtering can deposited into the bottom of the holes ofblack silicon. But the plating has poor compactness and bad uniformity.③the NiPalloy sheet that was prepared by electroless deposition can fill the holes of black siliconcompletely, and they are uniform and compact very well.The results also indicate that the NiP/BS contact and the Ni/BS contact, which weretreated by rapid annealing, both have a linear symmetrically ohmic contactcharacteristic in the model of longitudinal I-V test. Owing to the high interface barrierand the limitation of preparation processes, the Al/BS and NiCr/BS contacts only showan approximate ohmic contact characteristic. The results in the test of ohmic contactresistance show that the specific contact resistivity of Ni/BS contact deposited bythermal evaporation is about2.02·cm². The black silicon specimens which wereprepared by traditional electroless deposition and by direct electroless deposition havelower contact resistivities, and the related specific contact resistivities are1.66×10^-1·cm²and1.32×10^-1·cm², respectively.