Hu, Yidan and Zhuang, Qiandong and Ni, Qiang and Marshall, Andrew (2026) InGaAs/GaAsSb Type-II superlattices grown on InP substrates for extended short-wave infrared photodetectors. Masters thesis, Lancaster University.
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Abstract
This thesis aims to explore the application feasibility of type II InGaAs/GaAsSb superlattice (T2SL) based on InP substrate epitaxial growth in extended shortwave infrared (e-SWIR) light detectors with a cut-off wavelength of more than 2.5 μm. The device structure was analysed by high-resolution X-ray diffraction (XRD), and the results showed that the superlattice had good crystallization quality and layer periodicity. Photoluminescence (PL) experiments further revealed the bandgap properties of the absorbing layer, with emission wavelengths consistent with the designed cut-off wavelength. The prepared PIN light detector exhibited a wide spectral response in the range of 2.25 to 6 μm, with a peak response between 1–1.5 μm, and its cut-off wavelength was consistent with the PL results, demonstrating the effectiveness of the type II InGaAs/GaAsSb SL absorbing layer. Compared to commercial devices, the best performing device in the A1769 wafer exhibited higher photo response intensity, but the response curve has slight fluctuations, which may be due to insufficient material uniformity. These results indicate that InP-based type-II InGaAs/GaAsSb superlattices have application potential in high-sensitivity e-SWIR light detectors, but they still need to be further optimized in terms of material uniformity and device fabrication process.