(Invited) Increasing the Bandwidth of Semiconductor Photodetectors through Hot Carrier Generation in Nanometer-Scale Optical Coatings

Wednesday, 4 October 2017: 16:00
Chesapeake E (Gaylord National Resort and Convention Center)
L. J. Krayer (Department of Electrical and Computer Engineering, University of Maryland, College Park) and J. N. Munday (University of Maryland, College Park)
Nanometer scale optical coatings have recently been developed with tunable, high absorption through excitation of zeroth order Fabry-Perot (FP) modes. Such optical coatings have primarily increased above bandgap absorption in ultrathin semiconductor films with applications in thin film photodetection, photovoltaics and photocatalysis. We propose the use of zeroth order FP modes for expanding the bandwidth of semiconductor devices through sub-bandgap absorption in nanoscale metal contacts to semiconductors such as silicon. The absorption in the metal generates hot carriers that are injected into the semiconductor, enabling photocurrent generation from light with energy below the semiconductor bandgap energy. However, for efficient photocurrent injection, the metal must be highly absorptive at long wavelengths and ultra-thin in order for the hot carriers to reach the Schottky interface with enough energy to traverse the barrier. We show that by selecting materials with optical properties that satisfy a zeroth order FP mode (n ~ k for m = n + ik), it is possible to obtain ~80% absorption in materials as thin as 10-15 nm.