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Proceedings Paper

Dry etching, surface passivation and capping processes for antimonide based photodetectors
Author(s): Partha Dutta; Jeffery Langer; Vinay Bhagwat; Jasbir Juneja
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Paper Abstract

III-V antimonide based devices suffer from leakage currents. Surface passivation and subsequent capping of the surfaces are absolutely essential for any practical applicability of antimonide based devices. The quest for a suitable surface passivation technology is still on. In this paper, we will present some of the promising recent developments in this area based on dry etching of GaSb based homojunction photodiodes structures followed by various passivation and capping schemes. We have developed a damage-free, universal dry etching recipe based on unique ratios of Cl2/BCl3/CH4/Ar/H2 in ECR plasma. This novel dry plasma process etches all III-V compounds at different rates with minimal damage to the side walls. In GaSb based photodiodes, an order of magnitude lower leakage current, improved ideality factor and higher responsivity has been demonstrated using this recipe compared to widely used Cl2/Ar and wet chemical etch recipes. The dynamic zero bias resistance-area product of the Cl2/BCl3/CH4/Ar/H2 etched diodes (830 Ω cm2) is higher than the Cl2/Ar (300 Ω cm2) and wet etched (330 Ω cm2) diodes. Ammonium sulfide has been known to passivate surfaces of III-V compounds. In GaSb photodiodes, the leakage current density reduces by a factor of 3 upon sulfur passivation using ammonium sulfide. However, device performance degrades over a period of time in the absence of any capping or protective layer. Silicon Nitride has been used as a cap layer by various researchers. We have found that by using silicon nitride caps, the devices exhibit higher leakage than unpassivated devices probably due to plasma damage during SiNx deposition. We have experimented with various polymers for capping material. It has been observed that ammonium sulfide passivation when combined with parylene capping layer (150 Å), devices retain their improved performance for over 4 months.

Paper Details

Date Published: 31 May 2005
PDF: 8 pages
Proc. SPIE 5783, Infrared Technology and Applications XXXI, (31 May 2005); doi: 10.1117/12.605330
Show Author Affiliations
Partha Dutta, Rensselaer Polytechnic Institute (United States)
Jeffery Langer, Rensselaer Polytechnic Institute (United States)
Vinay Bhagwat, Rensselaer Polytechnic Institute (United States)
Jasbir Juneja, Rensselaer Polytechnic Institute (United States)

Published in SPIE Proceedings Vol. 5783:
Infrared Technology and Applications XXXI
Bjorn F. Andresen; Gabor F. Fulop, Editor(s)

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