Heterojunction of Bi2Se3 and Epitaxially Grown GaN Nanostructures on Oxide-Based Substrates for Self-Powered Broadband Photodetectors

Over the past decades, in addition to conventional Si-based devices, significant efforts have been made to explore stable compound semiconductor materials (SiC, III-V compounds, and various oxides) and their applications. Among these, GaN-based devices have been widely adopted and commercialized successfully, as GaN possesses chemical inertness, high electron mobility, a wide energy band gap (3.4 eV), etc. However, previous research on GaN UV photodetectors has primarily focused on GaN grown in the polar direction, which faces performance limitations due to spontaneous and piezoelectric fields. Further, while significant progress has been made in examining the photodetection properties of GaN grown on conventional dielectric materials like SiO2 and Al2O3, there remains an unexplored area in examining these properties on unconventional oxide substrates such as MgO, LiAlO3, SrTiO3 (STO), etc. Due to their incompatibility at high GaN growth temperature (800-1000 ℃) required by conventional techniques (MOCVD, MBE, HVPE, etc.). Further, the optical radiation detection range of GaN is confined to the ultraviolet region. For practical optoelectronic applications, photodetectors capable of detecting light across a wide wavelength range (300-1100 nm) with autonomous light-detection capabilities are essential. To address these issues, growing GaN along semi-polar and non-polar directions could improve the performance of GaN-based photodetector devices. Further, the photodetection properties of GaN grown on other lattice-matched oxide substrates can be explored using the LMBE technique, which can grow GaN at relatively low temperatures. Further, heterojunction semiconductors comprising a GaN in conjunction with a narrow bandgap material play a crucial role in developing self-powered multi-wavelength photodetectors. Recent advances in topological insulators offer promising prospects for quantum, electronic, and optoelectronic devices. Integrating these materials with GaN nanostructures paves the way for high-efficiency innovations. That spans nearly the entire spectrum of interest in photodetector exploration. Laying a foundation, this study first addresses the growth of GaN nanostructure on various plane orientations of sapphire using the LMBE technique. Further, we demonstrated the photodetection capability of single crystalline epitaxial GaN grown on STO at ≤ 600℃ using the LMBE technique. On the other side of the coin, we aim to make the heterojunction of the Bi2Se3 a topological insulator with LMBE-grown GaN nanostructures on sapphire and STO to fabricate highly responsive self-powered UV-Vis-NIR broadband photodetectors.<p></p>