A Study on Analysis Waveguide PIN Photodiode and InGaAs Layer Growth of using LPE System

For a long wavelength photodiode of optical communications, p-i-n diode, MSM(Metal-Semiconductor-Metal) diode, photoconductor, APD(Avalanche Photodiode) are used. And photodiodes with high efficiency and broad bandwidth are the key devices for feature wide-band optical communication systems. This device has problems of increasing quantum efficiency and transit time according to the increase of absorption in i-layer. Transit time can be reduced using by thin absorbing layer. The light injects toward the lateral direction in the WGPD(Waveguide p-i-n Photodiode) and widen bandwidth. A conventional surface-illuminated PD requires vertical mounting of the PD chip or 90o bending of input light by optical reflection in the module assembly. These complicated assembly procedures lead to a low yield and high assembly cost. On the other hand, a well-designed WGPD is usually passively aligned to the defined position on a module board, then flip-chip mounted without wire bonding. In this paper, the WGPD consists of two transparent InGaAsP guiding layers with refractive index of 3.39 at 1.3㎛ and a 1.5㎛ bandgap InGaAs with an index at 1.5㎛ of 3.59. The epitaxial layers were grown by horizontal LPE(Liquid Phase Epitaxy) apparatus on a n-InP substrate. i-InGaAs epi layer was grown at 630℃ with cooling rate 0.6℃/min by horizontal LPE apparatus. The growth thickness of i-InGaAs layer was about 1.3㎛ and these conditions were not satisfied. Because of source baking time were not enough as 6hr. And then, we did carry out source baking during a 24hr. It is that the condition of i-InGaAs layer were steadily getting better. For a long source baking time, the source's impurity concentration was reduced. In this case, i-InGaAs epi layer was grown at 630℃ with cooling rate 0.6℃/min. The process of growth was similar previous condition and these thickness was 1.5㎛. It could be found that the characteristics of WGPD fabricated by 24hr backing time were better than by 6hr. The fabricated device has an external quantum efficiency of 68% as well as a cut-off frequency of 4.5GHz at 1.55㎛ wavelength. For improving operation characteristics of WGPD, we need both transit time and frequency response. It is considered that the characteristics of the width, length, and thickness of waveguide photodiode's i-InGaAs layer. Moreover, I will suggest that a new waveguide structure and analysed using BPM(Beam Propagation Method) for increasing coupling efficiency between optical fiber and waveguide photodiode.제 1 장 서론 1 제 2 장 WGPD의 특성 5 2.1 PIN PD의 동작 원리 5 2.2 WGPD의 특성 8 제 3 장 WGPD의 설계 및 흡수층의 결정성장 16 3.1 WGPD의 설계 16 3.2 LPE 방법을 이용한 i-InGaAs/InP 결정성장 24 제 4 장 결론 39 참고문헌 4