| AVS 66th International Symposium & Exhibition | |
| Applied Surface Science Division | Thursday Sessions |
| Session AS-ThM |
| Session: | Advances in Depth Profiling, Imaging and Time-resolved Analysis |
| Presenter: | Nicole Kotulak, U.S. Naval Research Laboratory |
| Authors: | N.A. Kotulak, U.S. Naval Research Laboratory J.A. Nolde, U.S. Naval Research Laboratory M.E. Twigg, U.S. Naval Research Laboratory K.E. Knipling, U.S. Naval Research Laboratory D. Lubyshev, IQE Inc. J.M. Fastenau, IQE Inc. A.W.K. Liu, IQE Inc. E. Aifer, U.S. Naval Research Laboratory |
| Correspondent: | Click to Email |
Developing materials for mid-wavelength infrared (MWIR) photodetectors has been ongoing, with recent focus on structures that can operate at higher temperatures and across a larger portion of the MWIR range. In recent years, InAs/InAsSb strained layer superlattices (SLS) have been extensively studied and shown to achieve these performance parameters, out-performing the incumbent technologies [1]. Over the course of InAs/InAsSb SL development, as well as in similar Sb-containing device structures, it has been observed that Sb does not remain strictly within the intended layer [2-4].
The segregation of non-common-atoms at a growth interface and into the following layer leads to non-abrupt and asymmetric interfaces, which can cause changes to the optoelectronic properties of the SLS, including fundamental parameters such as band gap and effective mass [2,5,6]. For devices that rely on the precise engineering of the optoelectronic properties of the SLS in order to accomplish performance metrics, non-abrupt interfaces can, ultimately, detrimentally affect device performance, impacting suitability for specific tasks and environments [7]. Understanding the layer compositions at a near atomic-scale can enable these non-idealities to be included in bandstructure simulations to enable device design and optimization [8,9].
In this work, we use atom probe tomography (APT) to harvest 3D compositional data in an MWIR nBn T2SL photodetector consisting of 734 periods of alternating InAs and InAsSb, of which 31 total periods were analyzed. The resulting analysis shows a non-negligible concentration of Sb in the InAs layers, as well as a below-target Sb concentration in the InAsSb layers. While the background concentration of Sb stays consistent as growth of the T2SL progresses, there is an observable increase in the peak Sb concentration from the earliest-grown periods analyzed to the last-grown. These profiles demonstrate corroboration of a non-binary Sb profile observed using complementary techniques, and serve to assist in improving models of Sb-containing SLS for the development of high performance photodetectors.
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