Optimum carrier lifetime of semiconductor substrate in optoelectronic microwave grating structures

An analytical approach to the optimisation of substrate carrier lifetimes in optoelectronic microwave grating structures is reported. The method is based on the single-section approximation of the diffusion-controlled multisection grating profile, and utilises the specific slope behaviour to maximise the differential microwave reflection coefficient per unit length. The resultant optimum carrier lifetime is presented as a function of optical excitation wavelength, surface recombination velocity and grating centre frequency. In silicon, optimum values of roughly 10^-6-10^-5 s have been obtained