| This thesis addresses some of the inherent disadvantages of MSM photodetectors, in the interest of obtaining an optimized technology on GaAs and InP. The planar structure of the MSM detector, coupled with the sub-optimal electronic surface characteristics of III-V semiconductors, has resulted in a lack of performance reliability and predictability. Deleterious surface effects were reviewed, and techniques for minimizing these effects were investigated experimentally. For MSM detectors operating at 1550 nm wavelength, two material systems were compared. An InGaAsP/InP device with a pseudomorphic InGaP cap layer produced state-of-the-art performance. A 3 dB bandwidth of 12 GHz was determined in the frequency domain, for a finger spacing of 2 {dollar}mu{dollar}m, and an active region area of (100 {dollar}mu{dollar}m){dollar}sp2{dollar}. On InAlGaAs/InP, the passivating effects of a suitable surface etch, followed by deposition of silicon nitride, are presented.; For operation at 800 nm wavelength, an optimized AlGaAs/GaAs epitaxial structure was investigated, based on a theoretical treatment of hole pileup at the cap layer heterojunction. Subsequently, 18 GHz bandwidth at 2 to 3 V bias was demonstrated experimentally for an MSM detector with 1 {dollar}mu{dollar}m finger spacing, and an active region area of (50 {dollar}mu{dollar}m){dollar}sp2{dollar}.; Another disadvantage traditionally associated with MSM detectors is low responsivity, due to shadowing by opaque metal fingers. The second part of this thesis is dedicated to resonant-cavity techniques. Resonant-cavity epitaxial structures were designed in several material systems, for operation at 800, 1300, and 1550 nm wavelength. In particular, a novel device was fabricated in the InGaP/GaAs material system, employing a Burstein-Moss shifted mirror. Heavy n-type doping of GaAs shifts its band edge to approximately 810 nm wavelength, extending its transparency into a range where the most ubiquitous sources operate.; Finally, significant progress towards the realization of broadband photodetector arrays was made. Transmission-line concepts were used to design impedance-matched MSM photodetector arrays (IMMPA); the arrays are configured as loaded transmission lines, with characteristic impedance matched to the external load. A uniform 12 GHz bandwidth was obtained, for an array of 8 MSM photodetectors on GaAs. A full theoretical treatment is provided, and several diverse experiments were conducted to verify the theory. |
