Fabrication of high-multiplication InP avalanche photodiode and current-matched triple-junction GaAs solar cell

• Main Authors: Jheng-Jie Liu, 劉政杰
• Other Authors: 何文章
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/y29cjk

博士 === 國立臺北科技大學 === 光電工程系研究所 === 102 === In this thesis, the fabrication and performane characterization of InP-based SAGCM APD with InP/InAlAs hetero-structure avalanche layer and the triple-junction GaAs-based solar cells with the subwavelength nanopillars and graded-Index anti-reflection coating (ARC) were proposed and demonstrated. The hetero-multiplication region is consisted of an InAlAs energy build-up layer and an InP multiplication layer. InAlAs layer is mainly to make the energy promotion. When the potogenerated holes went into the high electric field InP avalanche region, the impact-ionization was immediately generation. The dark current-voltage (I–V), photo I–V characteristics and multiplication gains of APD were characterized from 25oC to -70oC. The capacitance-voltage (C–V) and 3-dB frequency response are also measured and compared. The maximum multiplication gain of 1012 at 25oC and of 3306 at −70oC were achieved, respectively, when the APD illuminated with an optical power of 1 nW at the wavelength of 1550 nm. Capacitance of 0.59 pF was obtained when biased at 0.9 Vbr and the gain-bandwidth product of 62 GHz also achieved in the propose APD structure. The epitaxial layers of the triple-junction GaAs-based solar cell were consisted of a GaInP top cell and a GaInAs middle cell. In general, the current mismatched between the GaInP subcell and GaAs subcell was generated after epitaxied growth. To improve current mismatched, two approaches of (a) SiO2-Nanopillars ARC structure and (b) hybrid deposition graded-index ARC two structures were proposed in this study. The experimental results show that (a) for a top cell current limited 3J-SC: using a SiO2-Nanopillars SiO2/TiO2 ARC on 3J-SC, a low and broad band reflective spectrum can achieve, especially exhibited at short wavelength region. Thus, the photocurrent generated in top cell was enhanced as well as the overall performance of 3J-SC was enhanced. (b) For a middle cell current limited 3J-SC: we proposed a hybrid deposition method to fabricated graded-index TiO2/SiO2 thin film to form a triple layer (TL) ARC. Before deposition these thin films, we also simulated the optical reflectance of TL ARC using TFCalcTM optical thin film software to obtain a low reflective band at the middle cell wavelength. Therefore, the photocurrent generated in the middle cell was enhanced due to a low reflectance exhibited at 680-950 nm wavelength band. Finally, the optical reflectance, EQE response, and photovottaic I-V were measured and compared. The results show that the proposed approaches were effectively improved the current mistmatched between the top and middle cell of 3J-SC and enhanced the overall photovoltaic performance of 3J-SCs.