Resonant Cavity Enhanced Photodiodes in the Short-Wave Infrared for Spectroscopic Detection

The design, fabrication and characterization of resonant cavity enhanced photodiodes for the short-wave infrared has been investigated. An InGaAsSb absorber and AlGaSb barrier were used in an nBn structure, within a Fabry-Perot cavity bounded by AlAsSb/GaSb DBR mirrors. The resonant cavity design produced a narrow response at 2.25 μm, with a FWHM of ~ 26 nm and peak responsivity of 0.9 A/W. The photodiodes exhibited high specific detectivities and low leakage currents at 300 K - 5 × 10
¹⁰
cmHz
^1/2
W
^-1
and 0.2 mAcm
^-2
respectively, with an applied bias voltage of -100 mV. A maximum specific detectivity of 1 × 10
¹¹
cmHz
^1/2
W
^-1
was achieved at 275 K and the detector continued to perform well at high temperatures - at 350 K the peak specific detectivity was 3 × 10
⁹
cmHz
^1/2
W
^-1
. The narrow resonant response of these detectors make them suitable for spectroscopic sensing, demonstrated by measurements of glucose concentrations in water. Concentrations as low as 1 % were discriminated, limited only by the associated electronic systems.