Two dimensional periodic grating light coupling in quantum well infrared photodetectors

Quantum Well Infrared Photodetectors do not respond to normal incident light due to the quantum mechanical selection rules associated with intersubband transitions, Thus alternate light coupling systems, such as gratings are required in order deflect the incoming light away from the normal. The resolution of the photolithography and accuracy of the etching become key issues in producing mailer grating feature sizes especially in shorter wavelengths. An enhancement factor of three due to 2D periodic grating fabricated on a QWIP structure was observed. Variation of the enhancement factor with groove depth and feature size of the grating can be theoretically explained.