Journal of the Korean Physical Society, Vol. 44, No. 4, April 2004, pp. L779∼L784 Letters Characteristics of a Planar InP/InGaAs Avalanche Photodiode with a Thin Multiplication Layer Kyung-Sook Hyun ∗ School of Electronics and Information Engineering, Sejong University, Seoul 143-747 Yong-Hwan Kwon Telecommunications Basic Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-600 Ilgu Yun Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Received 2 December 2003) We present a simple fabrication method for and the characteristics of a high speed InGaAs/InP avalanche photodiode (APD) with one floating guard ring. The APD structure that we propose consists of InP multiplication layer with a greatly reduced width and a highly doped electric field buffer layer, We also adopted a floating guard ring and a shaped main junction with recess etching for reliable operation of the APD. A long lifetime, exceeding ∼10 9 hours, was estimated from accelerated life tests. Also, reliable operation in the device center region was examined by measuring the two-dimensional gain. The gain and bandwidth product of the APDs was measured to be as high as 80 GHz. PACS numbers: 42.79.p, 85.60 Keywords: Photodetector, Avalanche photodiode, Breakdown voltage, Multiplication, Reliability, III-V semiconductor I. INTRODUCTION The use of avalanche photodiodes (APDs) in 10 Gbps systems is promising to satisfy the increasing demand for high-performance optical transmission systems. How- ever, several problems remain to be resolved for their use as high-speed optical detectors, including low re- liability and narrow structural margins for very high- speed responses. Many researches have focused on im- proving their performances via techniques such as band gap engineering and optimization of device structures in III-V compound semiconductors. Various APD struc- tures have been developed such as the InP/InGaAs sep- arated absorption, grading, charge, and multiplication (SAGCM) structure [1], the δ-doped SAGM structure [2], the InAlAs/InGaAs super-lattice structure [3,4], and the floating guard ring (FGR) structure [5–7]. Although these structures have offered large gain-bandwidth prod- ucts and high performances at 1.3 and 1.55 μm wave- lengths, their merits are greatly affected by variations in the fabrication parameters. Hyun et al. studied the breakdown characteristics of an InP/InGaAs APD with ∗ E-mail: kshyun@sejong.ac.kr; Tel: +82-2-3408-3792; Fax: +82-2-3408-3666 a p-i-n multiplication layer, and Park et al. calculated the effective thickness of the multiplication layer width in an APD [8,9]. Yuan et al. reported on the impact ion- ization characteristics of III-V semiconductors for a wide range of thicknesses in the multiplication region [10]. In this paper, we propose a simple fabrication method for a floating guard ring APD and demonstrate its char- acteristics. We report on the first achievement of In- GaAs/InP avalanche photodiode (APD) with a simple fabrication method and good performance, related to thin multiplication layer width. The APD with a shaped main p-junction and one floating guard ring was achieved through a finely controlled recess depth/width etching and one-step sealed-ampoule diffusion method. The fab- rication parameters of recess etching depth and diffusion time were varied to observe the electrical and the opti- cal characteristics in APD. As a detector, APDs should have a low dark current, less than 1 nA, good photocur- rent gain characteristics, long lifetimes of more than 10 5 hours, and a speed specification. Thin multiplication layer (about ∼ 0.3 μm) is crucial to satisfy these require- ments. However, a thin multiplication layer is difficult to obtain in the fabrication process for a planar structured APD. Even if it were obtained, suppression of the high electric field around the peripheral region while main- -L779-