Revealing Self‐Driven Broadband Photodetection Using Heterojunction of Bi₂Se₃ and Low‐Temperature Laser Molecular Beam Epitaxy Grown GaN on SrTiO₃ (100) Substrate

Abstract Optoelectronic properties of GaN are underexplored on good lattice matching SrTiO 3 (STO) due to STO's instability at the high GaN growth temperatures (800–1100 °C) required by traditional techniques. Here, GaN is grown on STO (100) at lower temperatures (500, 600, and 700 °C) using the laser‐assisted molecular beam epitaxy (LMBE) technique, and their morphological, crystalline, optical, and photodetection properties are analyzed. Further, heterojunction of Bi 2 Se 3 thin film (bandgap of 0.3 eV) is formed on the highest photo‐responsive LMBE‐GaN/STO to fabricate a self‐powered broadband photodetector. The fabricated self‐powered heterojunction photodetectors device exhibits a high responsivity of 2.93 × 10 2 mAW −1 in ultraviolet region and a notable responsivity of 2.3 and 12 mAW −1 in visible and near‐infrared spectral regions, respectively. In addition, photoresponse properties of fabricated devices on bare LMBE‐GaN and its heterojunction are compared under UV light illumination. The photoresponsivity of heterojunction in UV region is estimated to be 3.05 × 10 4 mAW −1 , which is enhanced by 100% compared to bare LMBE‐GaN. Combining the unique optoelectronic properties of GaN and rigidity of STO, epitaxy of GaN on STO enables construction of robust photodetector devices. Further, Bi 2 Se 3 ‐functionalized GaN can provide self‐sufficient and high‐quality futuristic optoelectronics devices.