Germanium on silicon photonics

Silicon photonics technologies have the potential to overcome the bandwidth limitations inherent in electrical interconnect technology. Modulation technology which is efficient both in terms of size and energy is required if silicon photonics are to replace electronics for interconnect communications. Silicon germanium technologies have the potential to not only improve the performance of current semiconductor devices but to also extend the reach of semiconductor technology into new areas such as development of a room temperature THz laser. A novel process that allows easy fabrication of Ohmic contacts to moderately doped n-type Germanium has been developed. This process has the potential to allow the realization of new devices which have been previously hampered by non-Ohmic contacts or dopant segregation problems. This work reported in this thesis also includes the design and fabrication of Ge/SiGe QCSE devices. Thin barrier QCSE designs have been put forward as a potential way to produce a more energy efficient modulator. Simulations of the devices show that a design with 16 nm Ge QWs and 8 nm SiGe barriers can provide effective modulation covering the entire optical communications C band with less than 3 V DC offset and achieve a contrast ratio across the band of over 3 dB. It was also shown that despite the thin barriers the wavefunctions remain well confined to the QWs suggesting that even thinner barriers are possible. MQW structures with thin barriers were grown and photodiodes fabricated from them. While the wafers did not have barriers as thin as designed they were thinner than devices previously demonstrated. From photocurrent measurements it was shown that these MQW structures were able to effectively modulate light near the 1550 nm wavelength with better performance than devices found in the literature