Substrate orientation-controlled photoelectric properties of 213-nm GeO2 solar blind photodetectors

GeO₂ is recognized as an ultra-wide bandgap semiconductor with high thermal conductivity and carrier mobility, possessing the great development potential in the solar blind photodetection field. During the deposition, selected substrates with different lattice orientations can cause variations in physical properties of GeO₂ films, thereby influencing the performance of the GeO₂ solar blind photodetector (SBPD). Here, GeO₂ films were deposited on m and r-plane sapphire substrates using the magnetron sputtering method and 213-nm SBPDs have been developed by selecting the high-temperature annealed GeO₂ films. The GeO₂ SBPD fabricated on m-plane sapphire substrate exhibits more excellent performances including faster rise and fall times of 8.09 and 8.15 ms, a higher photo-dark current ratio of 237.03, a larger photoresponsivity of 2.76 A/W, and a higher detectivity of 1.87 × 10¹⁴ Jones. By constructing energy band structures of GeO₂ SBPDs, excellent device performances can be attributed to the less migration energy requirement induced by small band barriers. Moreover, it is also demonstrated the existence of the built-in electric field and the smaller lattice mismatch further improve the GeO₂ SBPD performance. Experimental results demonstrate effects of substrate orientation-controlled photoelectric properties of 213-nm GeO₂ SBPDs, providing a new option for solar blind detection applications.