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<p>The intrinsic infrared absorption of GaSb substrate has long been recognized as a critical limitation in the performance of long-wavelength infrared (LWIR) detectors. Although back-thinning of the substrate is commonly employed in focal plane array (FPA) fabrication, a systematic quantitative relationship between substrate thickness and detector performance has remained unclear. In this study, we applied a combined process of mechanical grinding and chemical polishing to progressively thin the GaSb substrate from its initial thickness down to 500&#xa0;μm, 400&#xa0;μm, 200&#xa0;μm, 100&#xa0;μm, 50&#xa0;μm, and 30&#xa0;μm, respectively. Photoelectric testing at 77&#xa0;K reveals a clear positive correlation between the extent of thinning and detector performance. Specifically, as the substrate thickness decreases, the optical transmittance in the infrared band increases significantly. At 30&#xa0;μm, the responsivity (Vs) and specific detectivity (D*) improves by 10.36% and 7.6% respectively, compared with the initial 500&#xa0;μm state. To further mitigate substrate-induced absorption losses, we selected CrO₃ etching solution with significant selectivities between GaSb and InAsSb to remove GaSb substrate, and achieved an FPA responsivity enhancement of 18.3%. Our work establishes, for the first time, a clear quantitative relationship between GaSb substrate thickness and Type-II Superlattice (T2SL)detector performance. The research findings indicate the potential application of the substrate removal technology in IR detector fabrication.</p>

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Research on the performance of InAs/GaSb superlattice infrared detectors via GaSb substrate thinning and etching

  • 期刊论文

  • 发表日期：

    2026年2月28日

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  • Fan Zhang,
  • Niwei Zhang,
  • Kun Wang,
  • Yanchao Zhang,
  • Xiaoning Guan,
  • Pengfei Lu

摘要

The intrinsic infrared absorption of GaSb substrate has long been recognized as a critical limitation in the performance of long-wavelength infrared (LWIR) detectors. Although back-thinning of the substrate is commonly employed in focal plane array (FPA) fabrication, a systematic quantitative relationship between substrate thickness and detector performance has remained unclear. In this study, we applied a combined process of mechanical grinding and chemical polishing to progressively thin the GaSb substrate from its initial thickness down to 500 μm, 400 μm, 200 μm, 100 μm, 50 μm, and 30 μm, respectively. Photoelectric testing at 77 K reveals a clear positive correlation between the extent of thinning and detector performance. Specifically, as the substrate thickness decreases, the optical transmittance in the infrared band increases significantly. At 30 μm, the responsivity (Vs) and specific detectivity (D*) improves by 10.36% and 7.6% respectively, compared with the initial 500 μm state. To further mitigate substrate-induced absorption losses, we selected CrO₃ etching solution with significant selectivities between GaSb and InAsSb to remove GaSb substrate, and achieved an FPA responsivity enhancement of 18.3%. Our work establishes, for the first time, a clear quantitative relationship between GaSb substrate thickness and Type-II Superlattice (T2SL)detector performance. The research findings indicate the potential application of the substrate removal technology in IR detector fabrication.