Detection of a high photoresponse at zero bias from a highly conducting ZnO:Ga based UV photodetector

Abstract

Ga-doped ZnO (GZO) based ultraviolet photodetectors (PDs) were fabricated by dual ion beam sputtering in metal-semiconductor-metal structure. The room-temperature operable PD demonstrated responsivity of 58 mAW-1 at zero bias, which is 15 times larger than that reported on similar material grown by other physical vapour deposition process, with the internal and external quantum efficiency values of ~22.5% and 37.4%. The unbiased photodetection is attributed to the tunnelling of electrons due to heavy doping of GZO and built-in electric field due to different barriers at two metal semiconductor contacts. The asymmetry in electrodes was investigated by temperature-dependent current-voltage measurements.

Investigation of Dual-Ion Beam Sputter-Instigated Plasmon Generation in TCOs: A Case Study of GZO

“…43−45 The XRD measurements prove a high structural quality of the GZO thin film grown at 300 °C, with a comparatively strong preferred orientation in the (002) crystal plane at 2θ = 34.3°. 46 This 2θ value is associated with the hexagonal wurtzite structure of ZnO and points toward a high c-axis-orientated growth of the films. The FWHM value of GZO is 0.2°, and the corresponding crystallite size value is 43.4 nm, as depicted in Figure 1c.…”

“…The electrical resistivity variation and carrier concentration trends are guided by the GZO thin film crystallinity. The mobility in a heavily doped ZnO is governed by several factors, such as grain boundary scattering, dislocations, ionized impurity scattering, charge–charge/charge–phonon interaction, etc. , Here, the carrier mobility has demonstrated a preliminary increase with increase in T g from 200 to 400 °C, as depicted in Figure d, which can be ascribed to the combined effect of a higher carrier concentration and a reduced resistivity originating from a higher concentration of the dopant Ga atoms. A further increase in T g to 500 °C results in carrier mobility reduction.…”

“…The electrical properties of the GZO thin film with the growth temperature ( T g ) are illustrated in Figure d. All of the GZO thin films exhibit a n-type conductivity, which can be ascribed to the substitution of Ga atoms into the Zn sites, thus contributing one free electron to the conduction band . Moreover, the GZO film resistivity decreases marginally when T g reaches 300 °C and the resistivity increases abruptly afterward with a higher T g .…”

“…All of the GZO thin films exhibit a n-type conductivity, which can be ascribed to the substitution of Ga atoms into the Zn sites, thus contributing one free electron to the conduction band. 46 Moreover, the GZO film resistivity decreases marginally when T g reaches 300 °C and the resistivity increases abruptly afterward with a higher T g . A minimum resistivity of 5.3 × 10 −4 Ω cm is obtained at 300 °C.…”

Tuning Optoelectronic Properties Through In‐Plane Arrangement and Point Defects in ZnO Nanorods as Prepared by Room‐Temperature DC‐Unbalanced Magnetron Sputtering

“…ZnO is one of oxide semiconductor materials, which attracts a lot of research interests because it has a direct wide bandgap (3.37 eV), vast potential for tuning the bandgap, and large excitonic binding energy (≈60 meV) at room temperature . This binding energy is higher than that of its competitor, i.e., GaN (≈25 meV) and ZnSe (≈20 meV) .…”