Abstract
As wide-bandwidth, high-capacity communications via optical fiber is demanded, high-speed optoelectronic devices for message transmission and reception play major roles in promoting overall system performances. In this dissertation, InGaAs edge-coupled photodiodes (EC-PDs) with a light funnel integrated (LIFI) in front of the coupling aperture, called LIFI EC-PD, have successfully fabricated based on the self-terminated oxide polish (STOP), the crystallographic slope etching of InP, and the self-aligned diffusion (SAD) techniques. The LIFI EC-PD presents not only a lower dark current density (~4.4 mA/cm2) but also a higher responsivity (~0.4 A/W) than that of the mesa EC-PD (27 mA/cm2 and 0.26 A/W, respectively). Furthermore, the thick oxide film serves as the funnel in front of active-region aperture to enhance the coupling efficiency and to lower the bonding pad capacitance down to 50 fF. The lowered bonding pad capacitance can be beneficial in designing a device with a higher transit-time-limited frequency response of beyond 30 GHz. The LIFI EC-PD with a 1-µm thick absorption layer exhibits a 3-dB bandwidth of 20 GHz and a responsivity of ~0.4 A/W. A further improved novel high-speed waveguide photodetectors (WGPDs) integrated with a light input tapered-SiOx facet exhibiting extremely low dark current density and high responsivity characteristics of 0.74 A/W from 0.39 A/W of the device without light input tapered-SiOx facet has successfully been developed. The novel WGPDs can have an enlarged coupling aperture with responsivities and reduced dissipative absorption, which result from the reflection of an InP-slope and a p-metal, and thus permit more light to enter its absorption layer. Accordingly, such ground-breaking WGPD, exhibiting a 3-dB bandwidth of 20 GHz with a coupling efficiency of 0.74 A/W at a wavelength of 1.3-μm under 132.5 μW illuminations, can explore a better manufacturing competence.