High-performance Schottky heterojunction photodetector with directly-grown graphene nanowalls as electrodes
Schottky heterojunction based on graphene-silicon structure is promising for high-performance photodetectors. However, existed fabrication process adopt transferred graphene as electrodes, suffering from process compatibility and metal catalyst pollution. In this report, photodetectors are fabricated using directly-grown graphene nano-walls (GNWs) as electrodes. Due to the metal-free growth process, GNWs-Si heterojunction with ultralow measured current noise of 3.1 fA/Hz1/2 is obtained, and as-prepared photodetectors demonstrate specific detectivity of 5.88×1013 cm Hz1/2/W and 2.27×1014 cm Hz1/2/W with measured and calculated noise current respectively in ambient condition, which is among the highest reported level for planar silicon schottky photodetectors. In addition, on/off ratio of 2×107, time response of 40 s, cut-off frequency of 8.5 kHz and responsivity of 0.52A/W are simultaneously realized. The ultralow current noise is attributed to the excellent junction quality with barrier height of 0.69 eV and ideal factor of 1.18. Furthermore, obvious infrared photoresponse are observed with black body test, and potential applications based-on photo-thermionic effect are discussed.