Evaporated Sex Te1- x Thin Films with Tunable Bandgaps for Short-Wave Infrared Photodetectors

Chaoliang Tan; Matin Amani; Chunsong Zhao; Mark Hettick; Xiaohui Song; Der-Hsien Lien; Hao Li; Matthew Yeh; Vivek Raj Shrestha; Kenneth B Crozier; Mary C Scott; Ali Javey

doi:10.1002/adma.202001329

Evaporated Se_x Te_1- _x Thin Films with Tunable Bandgaps for Short-Wave Infrared Photodetectors

Adv Mater. 2020 Sep;32(38):e2001329. doi: 10.1002/adma.202001329. Epub 2020 Aug 9.

Authors

Chaoliang Tan^{1

2}, Matin Amani^{1

2}, Chunsong Zhao^{1

2

3}, Mark Hettick^{1

2}, Xiaohui Song^{3

4}, Der-Hsien Lien^{1

2}, Hao Li^{1

2}, Matthew Yeh^{1

2}, Vivek Raj Shrestha⁵, Kenneth B Crozier^{5

6

7}, Mary C Scott^{3

4}, Ali Javey^{1

2}

Affiliations

¹ Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA, 94720, USA.
² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
³ Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA, 94720, USA.
⁴ The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁵ School of Physics, University of Melbourne, Melbourne, VIC, 3010, Australia.
⁶ Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Victoria, 3010, Australia.
⁷ Australian Research Council (ARC) Centre of Excellence for Transformative Meta-Optical Systems (TMOS), University of Melbourne, Melbourne, Victoria, 3010, Australia.

PMID: 32776369
DOI: 10.1002/adma.202001329

Abstract

Semiconducting absorbers in high-performance short-wave infrared (SWIR) photodetectors and imaging sensor arrays are dominated by single-crystalline germanium and III-V semiconductors. However, these materials require complex growth and device fabrication procedures. Here, thermally evaporated Se_x Te_1- _x alloy thin films with tunable bandgaps for the fabrication of high-performance SWIR photodetectors are reported. From absorption measurements, it is shown that the bandgaps of Se_x Te_1- _x films can be tuned continuously from 0.31 eV (Te) to 1.87 eV (Se). Owing to their tunable bandgaps, the peak responsivity position and photoresponse edge of Se_x Te_1- _x film-based photoconductors can be tuned in the SWIR regime. By using an optical cavity substrate consisting of Au/Al₂ O₃ to enhance its absorption near the bandgap edge, the Se_0.32 Te_0.68 film (an optical bandgap of ≈0.8 eV)-based photoconductor exhibits a cut-off wavelength at ≈1.7 μm and gives a responsivity of 1.5 AW^-1 and implied detectivity of 6.5 × 10¹⁰ cm Hz^1/2 W^-1 at 1.55 μm at room temperature. Importantly, the nature of the thermal evaporation process enables the fabrication of Se_0.32 Te_0.68 -based 42 × 42 focal plane arrays with good pixel uniformity, demonstrating the potential of this unique material system used for infrared imaging sensor systems.

Keywords: SexTe1- x thin films; focal plane arrays; photodetectors; short-wave infrared; tunable bandgaps.

Abstract

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