Off-Chip Coupling

It is interesting to note that the fantastic growth in semiconductor electronics is based on only a few concepts. The rst transistor was made from germanium (Ge) because of its rather low processing temperatures in comparison to silicon (Si). What was considered a disadvantage turned out to become the unbeatable lead of Si technology since silicon dioxide and related materials allow fabrication techniques such as parallel and planar processing (Grimmeiss and Kasper, 2009). Dramatic shrinkage in feature sizes and a corresponding increase in transistor numbers led to integrated circuits (IC), which are now, with their incredibly high complexity, the undisputed backbone of microelectronics. The indirect semiconductors Si and Ge suffered in their potential for optoelectronics from low radiative emission efciency and low absorption at the indirect band gap. The direct semiconductors, mainly from group III/V, were strong in that respect and they started to dominate optoelectronics with clear band gap emission, light emission diodes (LED) of high quantum efciency, and laser diodes with low threshold currents even at room temperature. This had a strong impact on many areas including long-distance information transmission via optical ber cables. With more mature fabrication technology, highpower lasers and LEDs entered manufacturing applications and lighting in vehicles and homes. Although optoelectronic integrated circuits (OEIC) are familiar on group III/V substrates, their integration complexity is much lower than that of their IC counterparts.