GaAs-based long-wavelength traveling-wave photodetector

GaAs-based high-speed photodetectors attract lots of attention in the past twenty years due to their maturity in material growth and processing. However their wide bandgap characteristic (830 nm) restricts their applications in fiber communication wavelength (1.3 μm to approximately 1.55 μm). Recently some research groups had demonstrated GaAs-based n-i-n, p-i-n waveguide type photodetectors operating at 1.55 μm by taking advantage of the mid-gap defect absorption of low-temperature grown GaAs (LTG-GaAs). In this paper we propose and analyze different bandwidth-limiting factors for LTG-GaAs based metal-semiconductor-metal traveling wave photodetector (MSM TWPD) for both long and short wavelength cases. According to our calculation results, MSM TWPDs release the bandwidth limitation bottleneck in previous n-i-n and p-i-n TWPD structures, especially in the long wavelength case. Our analysis indicates that LT-GaAs based traveling-wave photodetectors can offer excellent bandwidth as well as high saturation power performances in fiber communication wavelength, which corresponds to long absorption length regime.