Low voltage episide down bonded mid-IR diode optopairs for gas sensing in the 3.3–4.3 μm spectral range

We describe “flip chip bonded” In(Ga)As and InAsSb heterostructure photodiodes and light emitting diodes (LEDs) (λ=3.3–4.3 μm) grown onto n-InAs substrate. The advantages of the construction include the possibility of coupling with immersion lenses through the contact free surface. The report presents I–V characteristic, spectral emission and responsivity, and simulations of sensitivity of the optically coupled diode pair to methane and carbon dioxide gases.