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Proceedings Paper

Analysis of surface and bulk effects in HgCdTe photodetector arrays by variable-area diode test structures
Author(s): Yi Deng; Chun Lin; Xiaoning Hu
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Paper Abstract

This study describes variable-area diode data analysis of surface and bulk effects of HgCdTe infrared photodiodes passivated with dual-layer CdTe/ZnS films. We attempt to present a general analytical relation between the zero-bias resistance-area product and the perimeter-to-area ratio of the diodes by variable-area diode array test structures. We have taken contributions into consideration from surface leakage between HgCdTe and passivant due to band bending, surface generation currents in the depletion region close to the HgCdTe-passivant interface, and the bulk currents. The model we use is based on the one put forward by Vishnu Gopal. The variable-area diode data analysis can be of great practical help in identifying the various possible mechanism contributing to the surface leakage currents. Through data analysis and curve fitting, we can also get some other useful parameters (like junction depth), which can be the reference to other experiment results. The experimental samples we used range from 20μm to 200μm in size and include both square and circular diode geometries. The conventional boron implantation was used to form the p-n junction and Au was used for the metal pads. The insulating layers of CdTe and ZnS were both electron-beam evaporated at a rate of 1.3 Å/sec. The fabricated diode test patterns were wire-bonded and packaged into a dewar system. I-V measurements were performed using a Keithley 4200 parameter analyzer. The data analysis and curve fitting are all dealt with by MATLAB. Through the results we can find that the surface leakage is nearly the same to the bulk current in diameter between 50~150μm, which indicate that surface leakage is still a dominating dark current in small dimension diode. The results also showed that diodes from 50 to 150μm in size have better performance than the larger or smaller ones and this can be explained by the limit of material imperfection and the limit of processing techniques.

Paper Details

Date Published: 5 August 2009
PDF: 7 pages
Proc. SPIE 7383, International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Infrared Imaging and Applications, 73834D (5 August 2009); doi: 10.1117/12.830924
Show Author Affiliations
Yi Deng, Shanghai Institute of Technical Physics (China)
Graduate School of the Chinese Academy of Sciences (China)
Chun Lin, Shanghai Institute of Technical Physics (China)
Xiaoning Hu, Shanghai Institute of Technical Physics (China)


Published in SPIE Proceedings Vol. 7383:
International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Infrared Imaging and Applications

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