Textbook in PDF format This book introduces and experimentally demonstrates a novel approach to exploit internal photoemission (IPE) for photodetection in silicon. The resulting device represents the first IPE-based detector that operates at technically viable performance figures. It combines a compact footprint and a high bandwidth with monolithic cointegration in silicon photonic circuits. The new concept opens an attractive route for optoelectronic generation and detection of waveforms in the sub-THz and THz range