J. Eur. Opt. Society-Rapid Publ. 2026, 22, 39 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026038 Available online at: https:// jeos. edpsciences. org
EOSAM 2025 Guest editors: Omar El Gawhary, Stefan Witte, Ignacio Moreno
Journal of the European Optical Society-Rapid Publications
RESEARCH ARTICLE
Numerical modeling of InGaAs / AlGaAs heterostructure for short-wave infrared nBn photodetectors
Çağrı Tok 1, 2, *
, Mert Satılmısß 1, Habibe Kelesß 1, 5, Fikri Oğuz 1, Hüseyin Sarı 2, and Ekmel Özbay 1, 3, 4 1 Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey 2 Department of Physics Engineering, Ankara University, 06560 Ankara, Turkey 3 Department of Physics, Bilkent University, 06800 Ankara, Turkey 4 Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara, Turkey 5 Department of Materials Science and Nanotechnology Engineering, TOBB University of Economics and Technology, Ankara 06560,
Turkey
Received 29 December 2025 / Accepted 8 April 2026
Abstract. nBn infrared photodetectors have emerged as a strong alternative to conventional pn and pin-based structures due to their low dark current, fast response, and suppression of Shockley – Read – Hall( SRH) generation pathways. In this study, an InP-based InGaAs / AlGaAs / InGaAs nBn heterostructure was designed and numerically analyzed using SILVACO TCAD at 300 K to investigate its electro-optical behavior under various bias conditions. The effects of barrier thickness and band alignment engineering were systematically evaluated with a particular focus on minimizing the effective valence band offset and blocking majority-carrier leakage without hindering photocarrier transport. The simulated band diagrams confirm that the AlGaAs barrier layer enables efficient majority-carrier suppression while maintaining low-resistance conduction paths for photogenerated carriers. As a result, the proposed device exhibits low dark current and high responsivity performance comparable to planar InGaAs structures even under low bias operation. These results highlight the significance of optimized barrier design in achieving high detectivity without relying on complex fabrication routes. Overall, the presented findings demonstrate the potential of tailored nBn architectures for next-generation short-wave infrared imaging, low-photon-flux sensing, and high-dynamic-range optoelectronic systems.
Keywords: nBn InGaAs, nBn SWIR, Low noise, SILVACO TCAD, Low dark-current, InGaAs / AlGaAs heterostructure.
1 Introduction
Short-wavelength infrared( SWIR) photodetectors have become pivotal components in modern optoelectronic systems, finding applications in defense imaging, medical diagnostics, environmental monitoring, and space-based instrumentation due to their high quantum efficiency and broad spectral coverage [ 1 – 3 ]. Among these, InGaAs-based detectors stand out for their low noise, lattice compatibility with InP, and high detectivity across the 0.9 – 1.7 lm range. However, conventional pn InGaAs photodiodes increasingly fall short in meeting the demands of next-generation imaging systems that require ultra-low dark current and stable operation at room temperature. In mesa-structured geometries, surface leakage and edge recombination effects dominate, while in quadrant-type devices with large active areas, dark current rises sharply, limiting the achievable signal-tonoise ratio [ 4, 5 ].
* Corresponding author: cagri. tok @ bilkent. edu. tr
To overcome these limitations, barrier-type architectures especially the nBn configuration have attracted significant research attention [ 6 – 8 ]. The nBn concept, consisting of an n-type absorber, a wide-bandgap barrier, and an n- type contact layer, aims to block majority carrier( electron) flow while allowing minority carrier( hole) transport with minimal resistance. This configuration effectively suppresses surface and generation – recombination( G-R) dark currents without introducing a depletion region in the absorber [ 9 ]. A key design challenge, however, lies in the selection of an appropriate barrier material. Recent studies have explored a variety of barrier layers, including AlGaAs, InAlGaAs AlGaAsSb, and GaAsSb compounds, yet conflicting results have been reported regarding their valenceband alignment and hole transport efficiency [ 10 – 13 ]. These discrepancies underline the need for further investigation into band alignment optimization for nBn structures operating in the SWIR range.
In this study, we design and simulate an nBn InGaAs SWIR photodetector incorporating a lightly n-doped
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