Electrical conduction mechanisms of CdTe quantum dots/p-si heterojunction

Abstract

CdTe quantum dots (QDs) are prepared on p-Si substrates using thermal evaporation technique. Current–voltage (I–V) characteristics of Au/CdTe QDs/p-Si/Al heterojunction are measured in a temperature range 304–368K. The results show that the device has a rectification behavior with a rectification ratio being 275 at ±1.5V. We determine the electrical conduction mechanisms of the heterojunction. At forward voltages V<0.3V, the thermionic emission becomes the main mechanism, where in this voltage range, it is possible to estimate the barrier height and the ideality factor. At a forward voltage range 0.5<V<0.9V, the conduction mechanism turns into the space charge limited conduction which is dominated by an exponential trap distribution (TSCLC). Within this voltage range 0.5<V <0.9, the total density of the trap states is calculated. At forward voltages 0.95<V<1.5V, Poole-Frenkel conduction mechanism fits well with the experimental data. It is found that there are two trap levels with zero fields of the activation energy which have values 0.16 and 0.46eV. At the reverse applied voltages, it is also found that the main source of the reverse current is the generation-recombination through p-Si rather than through the interface of the thin film itself.