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BPN895: Infrared Photodetectors Based on 2D Materials

Project ID BPN895
Start Date Sun 2018-Jan-28 21:31:36
Last Updated Wed 2018-Aug-08 16:06:28
Abstract Two-dimensional (2D) materials, particularly black phosphorus (bP), have demonstrated themselves to be excellent candidates for high-performance infrared photodetectors and transistors. However, high-quality bP can be obtained only via mechanical exfoliation from high-temperature- and high-pressure-grown bulk crystals and degrades rapidly when exposed to ambient conditions. Here, we report solution-synthesized and air-stable quasi-2D tellurium (Te) nanoflakes for short-wave infrared (SWIR) photodetectors. We perform comprehensive optical characterization via polarization-resolved transmission and reflection measurements and report the absorbance and complex refractive index of Te crystals. It is found that this material is an indirect semiconductor with a band gap of 0.31 eV. From temperature dependent electrical measurements, we confirm this band-gap value and find that 12 nm thick Te nanoflakes show high hole mobilities of 450 and 1430 cm2Vs at 300 and 77 K, respectively. Finally, we demonstrate that despite its indirect band gap, Te can be utilized for high-performance SWIR photodetectors by employing optical cavity substrates consisting of Au/Al2O3 to dramatically increase the absorption in the semiconductor. By changing the thickness of the Al2O3 cavity, the peak responsivity of Te photoconductors can be tuned from 1.4 um (13 A/W) to 2.4 um (8 A/W) with a cutoff wavelength of 3.4 um, fully capturing the SWIR band. An optimized room-temperature specific detectivity (D*) of 2 10^9 cm Hz1/2W is obtained at a wavelength of 1.7 um
Status Continuing
Funding Source
IAB Research Area NanoTechnology: Materials, Processes & Devices
Researcher(s) Matin Amani, James Bullock, Chaoliang Tan
Advisor(s) Ali Javey
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