We have previously developed an optically modulated high sensitivity heterostructure varactor whose C max /C min middot ratio of up to 113, and sensitivity of up to 35 are among the highest reported in the literature. These figures of merit indicate that this device is a good candidate for a number of applications including high order frequency multipliers. The device consists of a p-type delta modulation-doped heterostructure of AlGaAs/GaAs with Al 0.9 Ga 0.1 As/Al 0.24 Ga 0.76 As Distributed Bragg Reflectors (DBR) at the bottom producing a resonant cavity enhanced photodetector structure. As such the device has a dual role of being a sensitive photodetector and a Varactor. In fact, the response shows that the varactor characteristics can be optically modulated and depend on the intensity of the incident optical radiation. In this paper we present a lumped parameter model that captures the physics of the observed …