The Study Of High Speed 850nm Vcsel Array

With the continuous development of the Internet technology,the society has entered the era of big data with data center as the infrastructure,followed by the explosive growth of the amount of data transmission and the number of channels,which is the bandwidth and power consumption of data interconnection put forward higher requirements.In the field of high-speed interconnection of 100-meter-class high-speed interconnection,the trend of “bright-in copper retreat” cannot be reversed.At present,the industry mainly adopts an optical interconnection solution using a vertical cavity surface emitting laser(VCSEL)as a light source and a multi-mode optical fiber as a transmission link.The VCSEL is a semiconductor laser that emits laser light perpendicular to the substrate surface.It has the advantages of small size,circular output spot,single longitudinal mode output,low threshold current,low cost,easy integration into large area arrays,etc.The form of optical interconnection product includes active optical cables integrated with optical modules such as SFP+ and QSFP and module optical fibers.With the gradual maturity of the 400 G standard,the single-channel transmission rate has gradually transitioned from the original 10Gb/s,25Gb/s,to 50Gb/s,100Gb/s,and the modulation format has gradually transitioned from the binary non-return-to-zero code to the four-level PAM4 format.In this paper,set in the mass-production high speed VCSEL array,the key experimental resarch VCSEL array device in the process of high-speed manufacturing process.850 nm VCSEL array was fabricated based on the research of key processes,and its static characteristics and dynamics were tested and analyzed.The specific research work of this paper is summarized as follows:1.Introduce the working principle of VCSEL laser;The internal factors that limit the modulation characteristics of high-speed VCSELs are analyzed from the characteristics of semiconductor lasers by the rate equations;The effect of RC parasitic parameters on the high-speed characteristics of the device is analyzed by establishing an equivalent circuit model of a high-speed VCSEL device.The structure of high-speed VCSEL active region is introduced,and the effects of single and double oxide layers on parasitic capacitance parameters are calculated and analyzed.02.Research on manufacturing process of high-speed VCSEL arrays,The wet oxidation process in the manufacturing process of high-speed VCSELs was mainly studied.The principle of wet oxidation was theoretically analyzed.The influence of chamber temperature and gas flow rate on the oxidation rate in the wet oxidation process was experimentally studied.The effects of oxide layers with different aluminum compositions on the shape of the oxide pores were studied.The problem of uniformity in the wet oxidation process and some unusual problems in the process were analyzed.3.The process flow of dry etching and the basic principle of dry etching are introduced in detail.The effects of different etching parameters on the etch angle and etch rate of the mesa were experimentally studied,and the best process parameters were obtained.The extent of dry etching on the surface of the epitaxial wafer was studied.4.Introduce the metal process of VCSEL and the principle of ohmic contact in detail;The effect of different annealing parameters on the ohmic contact resistivity was studied by using CTLM and the optimum annealing process parameters were obtained.5.The characteristics of benzocyclobutene(BCB)resin and the process flow of VCSEL planarization are introduced in detail.Through experiments comparing the etching process of BCB under different mask materials,the best mask material was obtained.6.First,the electrical distribution and related uniformity of the fabricated VCSEL chip devices were analyzed in the wafer level.Second,the P-I-V characteristics,spectral characteristics,and far-field divergence angle characteristics of high-speed VCSELs are analyzed with a single array device.Finally,the dynamic characteristics of the high-speed VCSEL are analyzed from the small-signal modulation bandwidth and the large-signal pulse eye diagram.The-3dB bandwidth of single-channel is up to 17 GHz,and the back-to-back eye diagram is tested at 25Gb/s under the NRZ modulation mode and 50Gb/s under the PMA4 modulation mode.The transmission rate of high-speed VCSEL devices also get 200 Gb / s transmission rate of 1 × 4 VCSEL array under the PAM4 modulation mode.