GRATING-COUPLED QUANTUM-WELL INFRARED DETECTORS - THEORY AND PERFORMANCE

A theory of the grating-coupled quantum-well infrared detector, based on the modal expansion method (MEM) is presented together with numerical simulation results. MEM is a near-exact way of determining the electromagnetic-field pattern in a reflection grating-coupled quantum-well infrared detector, and is suitable for the calculation of absorption quantum efficiencies. Both lamellar gratings and crossed (doubly periodic) gratings are dealt with. Numerical simulations show that quantum efficiencies integrated with respect to wavelength eta(int) equal to 1-mu-m may be obtained in a detector equipped with a crossed grating of square symmetry, and a waveguide. The waveguide is defined by the metal grating on one side of the infrared absorbing quantum wells, and a thick aluminum arsenide layer on the other. This implies a factor of 4 higher eta(int) than in a 45-degrees polished edge detector with the corresponding quantum-well characteristics. Finally, a sensitivity analysis shows that a change in grating dimensions of the order of 0.1-mu-m results in relative changes of eta(int) of about 1%.