Improvements of AlGaN/GaN p-i-n UV sensors with graded AlGaN layer for the UV-B (280-320Â nm) detection

AlxGa1−xN/GaN p-i-n UV sensors grown by metal organic chemical vapor deposition (MOCVD) were fabricated for the UV-B (280-320 nm) detection. With a proper structure design by including a thin top p-layer and a graded AlxGa1−xN (x = 0.26 → 0.13) layer, the etching pit density (EPD) and the specific contact resistance of top p-layer can be significantly decreased. Device dark current density decreased from 3.5 × 10−7 to 2.49 × 10−11 A/cm2 at −3V and the spectrum responsivity at 310 nm UV-B range is 0.04 A/W, which is much better than traditional AlGaN-based devices without graded layer design.