High-speed position-sensitive devices: Theory and experiments.

摘要

Desirability for measurement of the correct high speed illuminated position becomes increasingly important in many applications. Using conventional position-sensitive devices (CPSDs), the illuminated-position can not be measured accurately. In search for measuring the fast illuminated-position, we are led to perform the study from two directions: (i) development of the new generalized model for one-dimensional (1-D) and two-dimensional (2-D) CPSDs to predict the performance characteristics in high-speed illuminated position measurement and (ii) proposing novel structures for the high-speed position-sensitive devices (HPSDs).;The generalized models for 1-D and 2-D CPSD are derived based on the well known RC-transmission line approximation. The novelty of these generalized models lie in obtaining direct results for any kind of excitations, illuminated on CPSD. These model equations are used in analysis and prediction of dynamic performance of the very short-pulse (impulse-like) excitation of 0.2T;After this essential work on CPSD, study on HPSD is carried out proposing two novel structures. In the first, CPSD response-speed is improved using a mesh type resistive layer, a new structure for HPSD reducing junction capacitance. This concept making HPSD is verified, and compared with CPSD, fabricated using the same IC technology. Again, a theoretical based design strategy is proposed for investigating effects of the principle design parameters on device performances and to select the optimum design parameters for mesh-type PSD (MEPSD). Results indicate that MEPSD can be designed to operate one- to two-orders in magnitude faster than CPSD. In the second on study of HPSD, a novel structure consisting of matrix-structured photodetectors is proposed. This HPSD can detect illuminated position binarily. In the binary PSD (BPSD), each element is individually excited with illumination, and response-speed is dependent on speed of each element. For laboratory demonstration, an 8 x 8 matrix is chosen for the BPSD, fabricated using an a-Si technology and was verified the operation of newly proposed BPSD.