Lateral and vertical microstructure enhanced photodetectors and avalanche photodetectors are monolithically integrated with CMOS/BiCMOS ASICs and can also be integrated with laser devices using fluidic assembly techniques. Photodetectors can be configured in a vertical PIN arrangement or lateral metal-semiconductor-metal arrangement where electrodes are in an inter-digitated pattern. Microstructures, such as holes and protrusions, can improve quantum efficiency in silicon, germanium and III-V materials and can also reduce avalanche voltages for avalanche photodiodes. Applications include optical communications within and between datacenters, telecommunications, LIDAR, and free space data communication.