Abstract
The study of this thesis is to fabricate a-Si:H photo detector. Two main efforts of this thesis are (1) fabrication of a-Si:H films，(2) Schottky and M-I-S photo detector devices fabrication. In order to reduce the influence of the particulate formation in the preparation of a-Si:H films，high hydrogen dilution ration and pulse RF power were used for a-Si:H films fabrication. The particulate formations were decreased by using the pulse RF power. From analysis of the optical band gap and the photo to dark current ratio of a-Si:H film，the deposition conditions and the characteristics of a-Si:H films are as follows： A. Pressure：0.75torr. B. Temperature：275℃ C. RF power：20w D. Pulse frequency：16.6667Hz. E. SiH4：36sccm，H2：144sccm F. The optical band gap was around 1.7-1.8eV G. The photo to dark ratio was 5×105 H. The microstucture factor R：0.05 The configuration allows the deposition of high quality a-Si:H with a photosensitivity of 5×105，indicating the presence of low density of defects. The device structures of a-Si:H photo detector are Schottky and MIS diodes. The structure of Schottky diode is glass/To/ metal. The structure of MIS diode is glass/To/a-Si:H(n-i)/insulator/metal. In this thesis，we prepared photodiode of different structures， different intrinsic layer thickness，and different insulator layer thickness. The photo to dark current ratio at -5v were about 10E3 and the thickness of I layer is 2500Ǻ.The photo to dark current ratio at -5v were about 7×10E3 and the thickness of I layer is 3000Ǻ.The photo to dark current ratio at -5v were about 10E4 and the thickness of I layer is 4000Ǻ.The photo to dark current ratio at -5v were about 8×10E3 and the thickness of I layer is 5000Ǻ. The photo current of all the structures under the reverse bias larger than 1 V was over 1u A ，which could satisfy the requirement for the circuit design. The peaks of photo spectral response of the devices with I layer thickness of 2500Ǻ、3000 Ǻ、4000 Ǻ，and 5000 Ǻ were around 450nm，460nm，560nm，580nm.The photo spectral response of the devices was shown to be suitable for visible light detection.