A 2 Gb/s optical receiver with monolithically integrated MSM photodetector in standard CMOS process

Abstract

A monolithically standard complementary-metal-oxide-semiconductor (CMOS) optical receiver with a metal-semiconductormetal (MSM) photodetector is presented in this paper. An active-feedback transimpedance amplifier (TIA) with negative Miller capacitance is used to increase the bandwidth of the receiver. The MSM photodetector with high responsivity provides higher sensitivity for the optical receiver. The optical receiver implemented in chartered 0.35 μm process achieves a 1.7 GHz bandwidth due to the low capacitance of the MSM photodetector. 2 Gb/s optical data are successfully transmitted with a bit-error rate of 10 -9 at an optical power of -15 dBm. The power consumption of the receiver is 94 mW under a single 3.3 V supply. Communication systems have always been the subject of a lot of researches. Today however, the transmission of data is becoming the performance limiting action. To enhance the performance of the communication, an optical communication system is researched to solve problems in present communication system. Nowadays, the research of optical receiver has got much progress [1,2]. In recent years, a lot of researches of hybrid integration optical receiver were reported [3,4]. Because the cost of packaging and fabricating are reduced greatly in standard CMOS process, much more attention of optical receiver has been attached to the research of monolithically integrated CMOS optical receivers for low cost. For example, an 1 Gb/s optical receiver with a -6 dBm sensitivity for λ=850 nm in 0.35 μm standard CMOS process was first reported by Bell laboratory [5]. Nevertheless, the sensitivity of the silicon-based, standard CMOS optical receiver is still a bit low because of the disadvantage of silicon material. Therefore the low responsivity problem of silicon detector is to need solution urgently. In order to solve this problem, some *Corresponding author (email: xxd@tju.edu.cn) researches of high responsive MSM photodetector were reported. Li realized a MSM photodetector with the responsivity of 0.118 A/W in Si-based process [6]. Robert reported a MSM polysilicon photodiode with 0.35 A/W responsivity in 0.35 μm CMOS process [7].In this paper, a monolithically integrated optical receiver with a MSM photodetector is presented. Generally, the sensitivity of the receiver could be improved by increasing the responsivity of the photodetector. In order to solve the problem of the low responsivity, a MSM photodetector is adopted in this optical receiver. Since Schottky diode is a major-carrier device, a MSM photodetector based Schottky diode has higher responsivity and better frequency characteristic. Besides all, the MSM photodetector has an advantage of low capacitance per unit area. In addition, an active-feedback TIA is adopted in the receiver in order to improve the bandwidth of the receiver. The design of the MSM photodetector in standard CMOS processA MSM photodetector integrated in standard CMOS