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Hybrid integrated photodetectors with flat-top steep-edge spectral responses that consist of an Si-based multicavity Fabry-Perot (F-P) filter and an InP-based p-i-n absorption structure (with a 0.2 μm In(0.53)Ga(0.47)As absorption layer), have been designed and fabricated. The performance of the hybrid integrated photodetectors is theoretically investigated by including key factors such as the thickness of each cavity, the pairs of each reflecting mirror, and the thickness of the benzocyclobutene bonding layer. The device is fabricated by bonding an Si-based multicavity F-P filter with an InP-based p-i-n absorption structure. A hybrid integrated photodetector with a peak quantum efficiency of 55% around 1549.2 nm, the -0.5 dB band of 0.43 nm, the 25 dB band of 1.06 nm, and 3 dB bandwidth more than 16 GHz, is simultaneously obtained. Based on multicavity F-P structure, this device has good flat-top steep-edge spectral response.

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A novel long wavelength photodetector with dual-wavelength spectral response is designed and fabricated using a step-shaped Fabry-Pérot (F-P) filter structure. The step-shaped GaAs/AlGaAs distributed Bragg reflectors and the InP PIN photodetector are grown on a GaAs substrate using low pressure metal organic chemical vapor deposition. High quality GaAs/InP heteroepitaxy is realized by employing a thin low temperature buffer layer. The photodetector structure is optimized by theoretical simulation. This device has a dual-peak distance of 19 nm (1 558 and 1 577 nm). The 3-dB bandwidth of 16 GHz is simultaneously obtained with peak quantum efficiencies of 8.5% and 8.6% around 1 558 and 1 577 nm, respectively. Dual-wavelength photodetectors in the 1.3-or 1.55-µm wavelength regions have significant potential in opticalfiber communication systems, especially for numerous microplate-based applications that aim to reduce optical interference caused by crosstalk, dispertion, or other impact factors of energy transmission and loss in optical transmission systems [1−5] . The operation of dualwavelength response has been demonstrated in several structures, including a taper substrate [6] , two stacks of quantum-well structures [7] , and two photodiodes [8] . However, the attractive approach of realizing a dualwavelength photodetector with step-shaped Fabry-Pérot (F-P) filter has yet to be reported.Furthermore, the distributed Bragg reflectors (DBR) in these F-P filters have been made from various materials, such as AlInGaAs/InAlAs [9] , InGaAsP/InP [10] , metamorphic GaAs/AlAs [11] , and dielectric mirrors [12] ; however, they all have the common problem of poor refractive index contrast. Among these candidates, GaAs/AlGaAs are the most promising DBRs because of their good electronic properties, reasonably low carrier recombination rates, and good refractive index contrast. However, for long wavelength (from 1.3 to 1.8 µm) photodetector fabrication, the PIN structure is preferred to be InP based. Several approaches on integrating GaAs/AlGaAs DBRs with the InP-based PIN photodetectors have been investigated, such as employing a thin, low temperature buffer layer [13] , fusing the InP-based active region with GaAs-based DBRs [14] , and growing metamorphic GaAs/AlGaAs DBRs on InP-based materials [15] ; these have been realized in tunable photodetectors [13] , resonant-cavity-enhanced photodetectors [16] , and vertical-cavity surface-emitting lasers [17] , respectively. In this letter, we propose a novel dual-wavelength photodetector realized by integrating a step-shaped GaAs based F-P filter with an InP-based PIN photodetector. High quality GaAs/InP heteroepitaxy is realized using a thin, low temperature buffer layer. We design and fabricate monolithically integrated step-shaped photodetectors that exhibit high spectrum and speed responses. Figure 1 shows the proposed bottom-injection type photodetector with step-shaped F-P filter. The incident light passes through the step-shaped filter into the PIN photodetector. The GaAs-b...