A high contrast photonic detector semiconductor device

A high-contrast photonic detector semiconductor device comprising a first (i.e. emitter) region 1 with a first doping polarity; a second (i.e. base) region 2 with a second doping polarity; a third undoped or lightly doped region (i.e. intrinsic region) 3; a fourth region (i.e. second base region) 4 of the second polarity with a higher carrier density that the second region and connected to a capacitor; and a fifth (i.e. collector) region 5 with the first doping polarity; wherein the first, second, fourth and fifth regions have electrodes associated with them, alternatively the order of the first and third regions can be swapped (i.e. Figure 1). The use of the undoped region results in the noise at the device being reduced. As the fourth region is connected to ground via a capacitor this reduces capacitance between the fifth and second regions.