A Stable Porous Silicon Dielectric Reflector with a Photonic Band Gap Centred at 10μm

By pulsed anodic etching at low temperature, we prepared a porous silicon reflector with a photonic band gap centred in the long-wavelength infrared spectral region （centred at about 12 μm）. After proper oxidation process, the stable reflector structure, which can reflect electromagnetic wave from 8 μm to 12 μm （centred at 10 μm） within wide incidence angles （about 50°）, is obtained. The wavelength shift of absorption peak of Si-H and Si-O shows the influence of oxidation process and indicates the stability of oxidized porous silicon dielectric reflector, which offers possible applications for the room temperature infrared sensor.     

An Array of One-Dimensional Porous Silicon Photonic Crystal Reflector Islands for a Far-Infrared Image Detector

With the aid of photolithography, an array of one-dimensional porous silicon photonic crystai reflector islands for a far infrared image detector ranging from 10 μm to 14 μm is successfully fabricated. Silicon nitride formed by low pressure chemical vapor deposition （LPCVD） was used as the masking layer for the island array formation. After etching, the microstructures were examined by a scanning electron microscope and the optical properties were studied by Fourier transform infrared spectroscopy, the result indicates that the multilayer structure could be obtained in the perpendicular direction via periodically alternative etching current in each pre-pattern. At the same time, the island array has a well-proportioned lateral etching effect, which is very useful for the thermal isolation in lateral orientation of the application in devices. It is concluded that regardless of the absorption of the deposition layer on the substrate, the localized photonic crystalline islands have higher reflectivity. The designed islands structure not only prevents the cracking of the porous silicon layers but is also useful for the application in the cold part for the sensor devices and the iliterconnection of each pixel.