Near Infrared responsivity of silicon-based detectors is low for weak light absorption in the wavelengths exceeding 1000nm. For 1064nm wavelength applications, it is necessary to use thick Si wafers to manufacturing devices for higher NIR responsivity performance. However, this leads to high applied voltage, long response time, imposing limitations on device characteristics and applications. Black silicon (BS) appears very high absorptance of light from the near-ultraviolet (250nm) to the near-infrared (2500nm) wavelength region. And the black silicon detectors are many times more responsivity than conventional silicon detectors in the near infrared.
In this article, BS is prepared using non-mask reactive ion etching technique and PIN BS detectors are fabricated. It is indicated that there is a disordered layer that is 2.0μm -3.5μm thick and made up of pillars with 90nm-400nm in diameter and 200nm-600nm in spacing interval. The reflectance of BS is less than 7% in the wavelength from 400nm to 1100nm, and rises from 1040nm. The absorptance of BS sample prepared by non-mask reactive ion etching remains more than 93% from 400nm to 1040nm, and the absorptance of 60% is observed at the wavelengths longer than 1500nm. High temperature annealing does not deteriorate its light absorption performance. The front-illuminated and back-illuminated BS PIN detectors are structured. At the wavelength of 1064nm, the responsivities of front-illuminated and back-illuminated BS PIN detectors are improved from 0.30A/W to 0.43A/W and 0.58A/W respectively.
The morphology of interface between polysilicon and its thermal oxide is very important for the fabrication of charge-coupled device (CCD) image sensors. Poor quality of polysilicon/oxide interface may lead to leakage current, low charge transfer efficiency, image deficiency, and then reduce the product yield and device reliability. In this paper, the effects polysilicon/oxide interface morphylogy on thermal oxide breakdown characteristics of polysilicon grown by low-pressure chemical vapor deposition (LPCVD) are studied by means of scanning electron microscopy (SEM) and electrical measurement. The breakdown characteristics of the oxide are related to the polysilicon/oxide interface smoothness. As the smoothness of polysilicon/oxide interface becomes worse, the breakdown strength of thermal oxide of the polysilicon decreases. Doping process of polysilicon remarkably affects the smoothness of polysilicon/oxide interface and the breakdown strength of the oxide. Saturated doping of polysilicon improves the polysilicon/oxide interface smoothness, so the breakdown strength of polysilicon may increase.