Deep traps and persistent photocapacitance in p-SnO2/i-ZrxSn1-xO2/n-SnO2 p-i-n diodes

Abstract

Current-voltage characteristics in the dark and under illumination, capacitance-voltage characteristics and admittance spectra in the dark and under illumination were measured for two sets of p-SnO2:Mg/i-ZrxSn1-xO2/n-SnO2/n+SnO2:Nb structures. These data strongly point to the structures demonstrating clear-cut persistent photocapacitance behavior existing for temperatures above room temperature. The phenomenon is shown to be due to the centers in the i-ZrxSn1-xO2 layer. These centers are believed to be related to residual Nb donors coming from Nb doped SnO2 layers. The analogy is drawn between the above-mentioned effect and the persistent photocapacitance phenomena in n-type doped AlGaN films for varying Al compositions that have been convincingly explained in the literature as in fact due to some of the standard n-type dopants being DX-like centers with a high barrier for capture of electrons. For the two studied p-SnO2/i-ZrxSn1-xO2/n--SnO2/n+-SnO2:Nb samples the thermal ionization energy, the barrier for capture of electrons, the optical ionization energy of the centers responsible for persistent photocapacitance have been estimated. The results suggest that the photoresponsivity of the samples increases when increasing the Zr mole fraction closer to the value of x = 0.3 and the concentration of centers responsible for persistent behavior decreasing from some 1017 cm-3 to some 1016 cm-3.