The large difference between speeds of fastest phototransistor (135 GHz) and hetero-junction bipolar transistor (710 GHz) has brought important problem and challenges in designing and manufacturing of fast phototransistor. This problem is more prominent in the microwave region. New approaches are required for recognition of existing problems in the known structures for phototransistor and introducing strategies to improve its performance. In this paper, using of convoluted resonator and waveguide structure in optical detector as well as optical waveguide as an appropriate solution for phototransistor scaling and performance improvements are suggested.