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13 October 2010 Dry etching and surface passivation techniques for type-II InAs/GaSb superlattice infrared detectors
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Abstract
Two of the key challenges in the realisation of focal plane arrays based on type-II InAs/GaSb superlattices (T2SL) are the difficulty in achieving a good sidewall profile and the increased dominance of surface leakage current as the device dimensions shrink. We report the electrical and morphological results of test pixels for mid-wave infrared T2SL photodiodes etched using a Cl2/Ar based inductively coupled plasma reactive ion etching (ICP-RIE) process and passivated using SU-8 epoxy photoresist. The etch rate and sidewall surface morphology of GaSb, InAs, and InAs/GaSb T2SL materials are compared after dry etching under the same conditions, leading to the determination of an optimal etch rate. The effect of surface treatment using selected wet chemical etchants before passivation on the surface leakage current is presented. Limitations of the dry etching recipe and further improvement of the sidewall verticality and smoothness are also discussed. Good sidewall profiles and bulk-limited dark currents are demonstrated for T2SL photodiodes etched to depths between 1.5 and 3.5 μm with a pitch size down to 12 μm.
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Siew Li Tan, Yu Ling Goh, Sankha dip Das, Shiyong Zhang, Chee Hing Tan, John P. R. David, Nutan Gautam, Hasul Kim, Elena Plis, and Sanjay Krishna "Dry etching and surface passivation techniques for type-II InAs/GaSb superlattice infrared detectors", Proc. SPIE 7838, Optics and Photonics for Counterterrorism and Crime Fighting VI and Optical Materials in Defence Systems Technology VII, 783814 (13 October 2010); https://doi.org/10.1117/12.864787
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