Light effects on the frequency response of InGaAs/InP SAM-APD devices

The frequency response of separate absorption multiplication avalanche photodiodes is investigated regarding the wavelength of the light and the direction from which the light is injected into the absorption region. The results apply to multilayer structures with an absorption layer of In_0.53Ga_0.47As and an avalanche layer of InP. The frequency response of the whole structure is computer from the response of each layer using matrix algebra. It is assumed a constant ionization coefficient ratio and electron and hole saturation velocities. Better frequency response is obtained when the light is injected from the avalanche region, which is apparent for small values of the avalanche gain. For light incident from the absorption region side a slight increase in the bandwidth is observed when the wavelength changes form 1.3μm to 1.55 μm. For large values of the avalanche gain (M>25) the frequency response does not seem to be very sensitive to the light properties under investigation.