Keywords: CdO layers, cadmium oxide, porous silicon, photodetectors, PLD, electrochemical etching, pulsed laser deposition, photoconductivity, Iran, nanotechnology
CdO/PSi/Si photo detector
In spite of various works which were carried out on CdO and porous Si (PSi) separately, the interesting properties of CdO/PSi/Si system are not known well. In this work, we study the photoconductivity of deposited CdO layer on PSi/Si system. PS and CdO layers were prepared by electrochemical anodisation of p-type crystalline silicon and pulsed laser deposition (PLD) of cadmium oxide target. Then samples were annealed in air at 500°C to increase their optical transmissions to a value as large as 90% for wavelengths above 700 nm. The XRD study reveals that the annealed films are polycrystalline with grain size of about 25 nm. SEM micrograph of the CdO/PSi/Si system indicates that CdO layer has sub micron granular structure on nano-porous silicon structure. The spectral responsivity of the photodiodes was measured in Vis.-near IR region. The light sensitivity showed linear behaviour vs. reverse bias voltage from 0.1 V to 3 V. The dark and photocurrent characteristics of CdO/PSi/Si structure showed ms response time. Experimental data shows that samples have good response to near infrared wavelengths.