Influence of γ-ray exposure and dose dependent characteristics of (n)PbS–(p)Si hetero-structure

An (n)PbS–(p)Si hetero-structure was developed by preparing the lead sulfide (PbS) nanostructure thin films deposited on p-type Si wafer using the successive ionic layer adoption and reaction (SILAR) method. To investigate the radiation detection capability of (n)PbS–(p)Si hetero-structure. For this purpose, nanostructure, photoluminescence, optical bandgap and I–V characteristic have been examined with various γ-ray dose 0, 25, 50 and 75 kGy. X-ray diffraction of as deposited PbS comparing to the irradiated samples suggested that the crystalline is improved with the γ-ray up to 50 kGy dose. The morphology studies showed that the average sizes increased from 55 to 105 nm with increasing the incident γ-ray dose level and decreased with further increase of dose. Energy dispersive X-ray (EDX) analysis confirmed the elemental composition of the as deposited PbS thin films. The reflectance of the (n)PbS–(p)Si hetero-structure in the ultraviolent–visible–near infrared reflectance (UV–Vis–NIR) region reduced about 40% compared to as deposited sample. The band edge shifted to longer wavelengths with increasing dose level to 50 kGy, and the reverse trend is observed at 75 kGy dose. Photoluminescence (PL) spectra revealed that the (n)PbS–(p)Si hetero-structure received the lowest recombination rate at 50 kGy. The rectifying current–voltage (I–V) characteristics revealed impact of the γ-ray irradiation dose on the hetero-structure electrical parameters. The rectifying ratio and turn-on voltage reduced from 22.3 to 7.4 at 5 V, and 1.25–0.5 V with γ-ray irradiation, respectively. All ideality factors of as deposited and irradiated (n)PbS–(p)Si hetero-structure are greater than 4. The barrier height, series resistance exhibited minimum values (0.49 eV, 1.47 kΩ) and the largest saturation current 1.69 × 10^–4 A, at 50 kGy.