Lateral Junction Waveguide Type Photodiode for Membrane Photonic Circuits Daisuke KONDO 1 , Tadashi OKUMURA 1 , Hitomi ITO 1 , SeungHun LEE 1 , Tomohiro AMEMIYA 2 , Nobuhiko Nishiyama 1 , and Shigehisa Arai 1,2 1 Department of Electrical and Electronic Engineering, 2 Quantum Nanoelectronics Research Center, Tokyo Institute of Technology 2-12-1-S9-5 O-okayama, Meguro-ku, Tokyo 152-8552, Japan aria@pe.titech.ac.jp Abstract A lateral junction type photodiode grown on a semi-insulating InP substrate was realized by 3-step OMVPE growth. The responsivity of 0.27 A/W, 3 dB bandwidth of 6 GHz and 7.5 GHz at a bias voltage of 0 V and -2 V, respectively, were obtained for the stripe width of 1.4 μm and device length of 220μm. An error free transmissions up to 6 Gbps at 0 V were confirmed. Keywords- Photodiode, Waveguide, Lateral junction, Membrane photonic circuits. I. INTRODUCTION Higher computing performance has been achieved due to the progresses of device densities and operation speed by scaling down CMOS transistor size to follow Moore’s law. However, further performance improvement will be limited by both power consumption due to heat generation [1] of the global metal interconnect and operation speed due to the RC delay [2]. To solve this problem, a lot of works on an optical interconnection that replaces the electric wiring have been pursued [3]-[5]. Moreover, the optical interconnection is expected to have low electromagnetic noise property. To realize the optical interconnection on LSI, low power consumption and compact optical active devices such as lasers, amplifiers, and detectors are needed. For this demand, we have proposed a membrane distributed-feedback (DFB) laser, which consists of a thin (~ 150 nm-thick) semiconductor core layer including active regions with grating sandwiched by low-index polymer cladding layer [6]. The membrane structure has a strong optical confinement into the core layer and allows lasing operation with very low threshold. So far, a low threshold optical pump power (0.34 mW) with a stable single-mode operation was demonstrated under room-temperature continuous-wave (RT-CW) condition [7]. With the aim of realizing injection-type membrane lasers, a lateral current injection (LCI) structure [8] was adopted and RT-CW operation of LCI buried-hetero structure (BH) lasers with 400-nm-thick GaInAsP core layer grown on a semi-insulating (SI) InP substrate has been demonstrated [9],[10]. This membrane structure is also attractive for waveguide type photodiodes because the device length can be shortened due to its high optical confinement structure compared with previously reported photodetectors with a lateral junction [11], hence higher speed operation due to a feature of low capacitance will be expected. In this paper, we would like to present fundamental properties of a lateral junction waveguide type photodiode with thin current injection layer thickness. II. DEVICE STRUCTURE AND FABRICATION The schematic structure and the cross sectional SEM view of the fabricated device structure are shown in Fig. 1 and the fabrication process are shown in Fig. 2. An initial wafer with undoped GaInAsP core layers consisting of five quantum-wells (QWs, Ga 0.22 In 0.78 As 0.81 P 0.19 , 6 nm thick), barriers (Ga 0.26 In 0.74 As 0.49 P 0.51 , 10 nm thick) and optical confinement layers (OCLs, Ga 0.21 In 0.79 As 0.46 P 0.54 ), were prepared by organo- n-InP (4 10 18 /cm 3 ) p-GaInAs contact (8 10 18 /cm 3 ) p-InP (4 10 18 /cm 3 ) Ti/Au 1.4μm 220μm Ti/Au p-InP n-InP Fig. 1 The schematic structure and the cross sectional SEM view of the device.