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.

Absorption fingerprints of substances such as glucose, acetone and CO2 fall within the short-wave infrared range (SWIR), in the wavelength range 1.7 μm -2.4 μm; improved detection of these substances will be impactful to health, wellbeing and the environment. A design of detector based on the emerging material system InGaAsSb with cut-off wavelengths in this range, 2.25 μm, is presented. By controlling the composition of the InGaAsSb, the cut-off wavelength can be extended beyond GaSb (1.7 μm) to a particular target with minimal leakage increase. Unbiased operation has been obtained using a p-B-n structure design and a quasi-planar device design with good optical power resolution (40 pW). At the current state of optimisation, D* is 9.4×10 10 Jones at 0 V bias and 2.0 μm which is approaching the much more mature extended InGaAs technology, grown mismatched on InP, with the same cut-off wavelength. InGaAsSb is grown on GaSb substrates which are increasingly popular for IR optoelectronics and being lattice matched will offer a higher yield in production compared to mismatched growth. With InGaAsSb, the GaSb-matched material system can support lattice matched epilayers exhibiting cut-off wavelengths from the near to the longwave infrared. This work looks towards future applications through evaluations and measurements of low concentration glucose solutions. These detectors show great promise for future commercial applications.

An InGaAsSb p-B-n structure has been designed and characterized for zero bias low power detection applications. Devices were grown by molecular beam epitaxy and fabricated into quasi-planar photodiodes with a 2.25 µm cut-off wavelength. Maximum responsivity was measured to be 1.05 A/W at 2.0 µm, achieved at zero bias. D* of 9.4 × 1010 Jones was determined from room temperature spectra of noise power measurements with calculated D* remaining >1 × 1010 Jones up to 380 K. With a view to simple miniaturized detection and measurement of low concentration biomarkers, optical powers down to 40 pW were detected, without temperature stabilization or phase-sensitive detection, indicating the photodiode’s potential.