High-efficiency, Ge-on-SOI lateral PIN photodiodes with 29 GHz bandwidth

The lateral PIN photodetectors were fabricated using Ge films deposited on ultra-thin silicon-on-insulator (SOI) substrates. The starting material was produced by directly growing Ge on a thin SOI substrate with initial SOI thickness of 15 nm. Good agreement between theory and experiment was obtained, demonstrating the benefit of the SOI layer for limiting the Si and Ge interdiffusion during high-temperature thermal cyclic annealing (TCA) step. The bandwidth saturated at very low voltages, and even at zero bias, bandwidths as high as 20 GHz were achieved.