IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Monday Sessions
       Session TF-MoP

Paper TF-MoP5
Amorphous Silicon Photodiodes for Image Sensing

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Multilayers and Thin Film Characterization Poster Session
Presenter: Y. Kuo, Texas A&M University
Authors: M. Ristova, Texas A&M University and University in Skopje, Republic of Macedonia
Y. Kuo, Texas A&M University
H.H. Lee, Texas A&M University
S. Lee, Texas A&M University
J.Y. Tewg, Texas A&M University
Correspondent: Click to Email
The aim of this research was to develop amorphous silicon (a-Si:H) thin film photodiodes for image sensing using the He-Ne (632 nm) laser source. Three different kinds of thin film diode structures, i.e., metal-(a-S:H)-metal, n@super +@-(a-S:H)-metal, and n@super +@-(a-S:H)-n@super+@, were prepared. The a-Si:H (between 200 and 1000 nm) and n@super +@ (20 nm) layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 250°C. The molybdenum metal was deposited with a magnetron-sputtering gun at 13.56 MHz. All a-Si:H layers, which contain about 10 % of hydrogen, were deposited under the same condition. The n@super +@ layer's conductivity was about 2.3E10 (ohm-cm)@super -1@, while the conductivity of the undoped a-Si:H was about 1-2E9 (ohm-cm)n@super -1@. The complete diode was fabricated using photolithography and reactive ion etching (RIE) methods. Factors, such as electrode geometry, contact resistance, a-Si:H thickness, and the thermal treatment, were studied for their influence on the diode performance. The diode's dark and illumination currents, i.e., I@sub dark@ and I@sub illumination@, were determined from current-voltage (IV) measurement. The following conclusions are summarized from this study: 1) the highest current (in either dark or under illumination condition) can be obtained with the pattern with highest value for the ratio between the illuminated area and the average distance between the gridlines 2) the contact resistance can be the dominating factor in the current path, 3) the thick film has the large light absorption efficiency and the high current ratio, and 4) the annealing step repairs the RIE damaged film and greatly improves the diode performance.