A high-sensitivity, fast-response, rapid-recovery p-n heterojunction photodiode based on rutile TiO2 nanorod array on p-Si(1Â 1Â 1)

The growth and characterization of a p-n heterojunction photodiode were studied. This photodiode was based on rutile TiO2 nanorods (NRs) grown on p-type (1 1 1)-oriented silicon substrate seeded with a TiO2 layer synthesized by radio-frequency (RF) reactive magnetron sputtering. Chemical bath deposition (CBD) was performed to grow rutile TiO2 NRs on Si substrate. The structural and optical properties of the sample were studied by X-ray diffraction (XRD) and field emission-scanning electron microscopy (FESEM) analyses. Results showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were further examined by photoluminescence spectroscopy, and a high-intensity UV peak centered at around 392 nm compared with visible defect peaks centered at 527 and 707 nm was observed. Upon exposure to 395 nm light (2.3 mW/cm) at five-bias voltage, the device showed 2.9 × 102 sensitivity. In addition, the internal gain of the photodiode was 3.92, and the photoresponse peak was 106 mA/W. Furthermore, the photocurrent was 3.06 × 10−4 A. The response and the recovery times were calculated to be 10.4 and 11 ms, respectively, upon illumination to a pulse UV light (405 nm, 0.22 mW/cm2) at five-bias voltage. All of these results demonstrate that this high-quality photodiode can be a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.