Growth of InxGa1-xSb linearly graded buffers on GaSb substrate for ultra-low bandgap 0.1 eV InAsSb layer

• High-quality InAs 0.5 Sb 0.5 layer growth on InGaSb graded buffer/GaSb substrate. • A smooth surface was achieved by suppressing micro-pillar formation and phase separation. • A high degree of strain relaxation of 91 % was obtained even with 50 % Sb composition. • Absorption edge of 8 μm at room temperature was confirmed in InAsSb layer. Metamorphic growth of 0.1 eV InAs 1-x Sb x layers on GaSb substrates presents a promising pathway for the development of cost-effective and scalable long-wavelength infrared (LWIR) photodetectors. To address the lattice mismatch challenge between InAsSb and GaSb, a sophisticated metamorphic buffer design is essential. In this study, we report an optimized InGaSb linearly graded buffer layer to grow a high-quality InAsSb layer on a GaSb substrate. We focus on optimizing the growth temperature to relax residual strain and achieve a smooth surface morphology for potential LWIR detector applications. Raising the growth temperature from 400 °C to 450 °C effectively reduces micro-pillar formations and promotes a high degree of strain relaxation (> 90 %). In addition, we study effects of grading rates of InGaSb graded buffers on surface morphology and dislocation propagation. By varying the buffer thickness from 100 nm to 1000 nm, we also find that crystal defects such as stacking faults, threading dislocations, and phase separation can be minimized. This systematic approach provides valuable insights for the growth of high-quality 0.1 eV InAsSb layers on GaSb substrate for LWIR applications.