The analysis of current flow mechanism in CdS/CdTe heterojunction

Abstract

An analysis of current–voltage dependencies of CdS/CdTe heterojunction in the 78–370 K temperature range has been carried out. According to this analysis the current flow mechanism is determined by the tunneling processes through dislocations, which penetrate the heterojunction space charge region. The concentration of dislocations has been estimated as 2 · 10 5 cm − 2 . The number of steps necessary for tunneling varies: 2.5 · 10 2–1.7 · 10 3. The characteristic energy has a weak temperature dependence (− 0.2 meV/K) and its value vary 120–200 meV. The increase of the annealing duration results in the decrease of the characteristic energy. The multistep tunneling processes through local centres, determined by impurity centres, interface states and defects in the space charge region, predominate at reverse biases. The number of tunneling steps is 1–4 · 10 2. The concentration of local centres (traps) in the heterojunction have been estimated as 2.37 · 10 5–1.63 · 10 6 cm − 3 . The thermal annealing in the presence of CdCl 2 up to 60 min does not modify the current flow mechanism in CdS/CdTe heterojunctions.