Ferroelectric Liquid Crystal Light Valve Using SiO 2 / A-Si:H Photodiode
- PDF / 1,033,477 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 119 Downloads / 160 Views
FERROELECTRIC LIQUID CRYSTAL LIGHT VALVE USING Si02 / A-Si:H PHOTODIODE T. Horikawa, S. Tahata, S. Kaho, T. Masumi, N.Mikami, K.Takahashi, Materials & Electronic Devices Lab., and H. Nakajima, Z. Nishi, Industrial Electronics • Systems Development Lab., MITSUBISHI ELECTRIC CORP., Amagasaki, Hyogo Japan
M.Nunoshita,
ABSTRACT A new type of ferroelectric liquid crystal light valve (FLCLV) is presented. The design of the FLCLV is based upon the linear equivalent circuit analyses. A photosensor in the FLCLV consists of a metalinsulator-semiconductor (MIS) photodiode. A-Si:H doped with boron and nitrogen [a-Si:(:N:B)] is used in the MIS diode. The a-Si:H(:B:N) film has a dark-conductivity of less than ix10-'2 S/cm and a high photosensitivity. Consequently, the writing characteristics of the FLCLV for a two dimensional (2D) image are evaluated. Using writing light of 630 nm and i mW/cm2, a high resolution capability of 120~140 Ip/mm is obtained.
INTRODUCTION Real-time optical information processing and image projection require the development of spatial light modulators (SLMs) [1,2]. In these application, high sensitivity, high resolution capability, fast response and good output image uniformity are necessary for an SLM. In the latest years, many kinds of SLMs have been developed by numerous research groups [2-6]. Ferroelectric liquid crystals (FLCs) are a promising material for the SLM, because of high resolution capability and fast switching speed between their two stable states. As a photosensing material, cadmium sulfide [3], crystalline silicon [4], crystalline gallium arsenide [5] or amorphous silicon [2,6] has been used. Amorphous silicon is most widely used because of its advantages such as high photosensitivity for visible light and easy fabrication. Here, we propose a new type of FLCLV, which consists of an FLC layer and an MIS photodiode. An amorphous silicon film with a low darkconductivity is used in the MIS photodiode. A high resolution capability is achieved in the FLCLV. Firstly, in order to design the most suitable photosensing layer for a high performance FLCLV, we analyze numerically the device response by using the two equivalent electrical circuit models; These equivalent circuits for the FLCLV require an especially lower dark-conductance of the photosensor. A-Si:H(:N:B) film with a lower conductivity and the MIS photodiode structure are chosen for the photosensor satisfying the above constraints and realizing a high resolution capability. We will discuss the doping properties of a-Si:H(:N:B) film and the electric properties of the MIS diode. The structure and the fabrication of the FLCLV are described, and the 2D image written on the FLCLV is evaluated.
204
Numerical analyses We try the numerical analyses of the device response in two ways. The first analysis is for the transient change of the potential drop across the FLC crystal layer using a lumped element electrical circuit shown in fig.1. The second is for the static spatial potential distribution in the FLC layer, when a 2D image is proj
Data Loading...
