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Title:Antimonide-based type-II superlattices for infrared detection
Author(s):Kesler, Benjamin
Advisor(s):Chuang, Shun-Lien
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
infrared detection
type-II superlattice (T2SL)
metalorganic chemical vapor deposition (MOCVD)
Abstract:The vast array of applications for the detection of mid- to long-wave infrared radiation has spurred continuous interest in new and novel technologies to replace the current generation of state-of-the-art devices such as mercury cadmium telluride (MCT) detectors. One of the more promising alternatives is the type-II superlattice (T2SL), which was first proposed for infrared detection in 1978 and has been theoretically predicted to perform better than any MCT detector. Some advantages of the T2SL are its vastly improved electrical properties, material growth quality and cost, and the large number of degrees of freedom in tailoring the band structure to maximize performance at any given wavelength when compared to MCT detectors. However, the performance of T2SLs has been limited due to growth and fabrication problems, though the past decade has seen devices demonstrated with less than an order of magnitude difference in performance metrics when compared to commercially available MCT products, which is very promising for this material system. This thesis presents only the second generation of T2SL devices grown via metal-organic chemical vapor deposition (MOCVD), and the first generation of devices grown on an InAs substrate by either molecular beam epitaxy (MBE) or MOCVD, an important fact for flip-chip bonding applications due to the lower absorption coefficient of InAs in the infrared when compared to the more common GaSb substrates. MOCVD is the preferred growth method in the industry, when available, due to its fast deposition rates with only a minimal sacrifice in growth precision when compared to MBE, so it is imperative that MOCVD T2SL devices quickly demonstrate performances similar to MBE grown T2SLs. A peak specific detectivity of 7.62 x 10^9 Jones at approximately 8 um is reported, a 4.8 times increase from the value of 1.6 x 10^9 Jones for the first MOCVD grown T2SL (which was grown on a GaSb substrate). This thesis also addresses the reduction and elimination of surface leakage current, a dark current method that can be debilitating to device performance if not properly addressed. Promising results are achieved through the use of an ammonium sulfide soaking solution. In one instance, an almost one order of magnitude reduction of dark current densities is achieved using a neutralized ammonium sulfide solution, indicating that surface passivation is an important and necessary processing step. Future improvements, such as the usage of an encapsulating layer of polyimide or silicon nitride, are suggested in order to maintain the integrity of the ammonium sulfide passivation scheme and to physically protect the device itself.
Issue Date:2012-09-18
Rights Information:Copyright 2012 Benjamin Kesler
Date Available in IDEALS:2012-09-18
Date Deposited:2012-08

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