Temperature Dependence Of Voltage-controlled Negative Resistance And Electroluminescence In Al-al_2o_3-au Diodes

摘要

Voltage-controlled negative resistance (VCNR) and unipolar resistive switching that can be used for memory applications can develop in the current-voltage (I-V) curves of metal-insulator-metal diodes. Electroluminescence is intimately connected with the occurrence of VCNR in I-V curves. The temperature dependence of VCNR and electroluminescence of Al-Al_2O_3-Au diodes with anodic Al_2O_3 thicknesses between 12 and 54 nm has been studied between 300 and 180 K. There is a threshold voltage, V_(th), for the occurrence of electroluminescence. V_(th) is between 1.5 and 2.0 V at 300 K and is independent of Al_2O_3 thickness. As temperature is lowered, the maximum current of the I-V curve that exhibits VCNR, I_(mx), decreases. The voltage for maximum current, V_(mx), increases as does V_(th). Around 200 K, currents become small and erratic; VCNR and electroluminescence disappear but reappear if the diode temperature is raised above ～200 K. Detailed measurements of the temperature dependence of I_(mx), V_(mx), and V_(th) are presented for Al-Al_2O_3-Au diodes with different anodic Al_2O_3 thicknesses. The relative electroluminescent intensity is largest in the thinnest samples. A model is proposed for conduction in a filamentary region of an Al-Al_2O_3-Au diode. Electrons injected into an impurity band in Al_2O_3 recombine with defect centers in Al_2O_3 to produce electroluminescence. Positively charged defect centers in Al_2O_3 cause the formation of an Ohmic contact and a high-field region at the Al-Al_2O_3 interface. The Ohmic contact, in turn, determines the I-V curves of a conducting channel. Recombination of electrons with defect centers that produce the Ohmic contact changes the Ohmic contact and causes the current decrease in the negative resistance region of the I-V curves.