Contents 1. Introduction
The performance of microwave and millimeter-wave photonic systems would benefit from the use of photodiodes (PDs) with high saturation power, high-speed and high responsivity performance [1]. There are two major ways to satisfy these three requirements of PDs. One is to distribute and uniform the photocurrentsalong the edge-coupled PDs by improving the structure of optical and electrical waveguides, such as, velocity matched distributed photodetector (VMDP) with leaky optical waveguide [2] and evanescent coupled photodiode (ECPD) [3]–[5]; the other is to minimize the space-charge effect by changing the structure of epitaxial layers, such as uni-traveling carrier PD [1] and partially depleted absorber PD [6]. Recently, several research groups have demonstrated state-of-the-art performance of evanescent coupled PD with a short coupling length and partially depleted absorber [4], [5]. However, the tolerance of cleaving process of such devices is very small (less than ) and different length of coupling region will affect the performance of responsivity seriously [3]–[5]. For the case of PD with leaky optical waveguide, the problem of cleaving tolerance can be released greatly [2], but its electrical bandwidth is sacrificed for high responsivity performance due to that large device-absorption-volume is required to completely absorb the diluted optical power. In this paper, we demonstrate a novel structure of PD, which is composed of a leaky optical waveguide and a distributed-bragg-reflector (DBR). By incorporating such novel structure with partially depleted absorber, the demonstrated device can achieve much superior performance of speed, saturation power, and responsivity to the control without DBR mirrors.
