Mechanisms of carrier lifetime enhancement and conductivity-type switching on hydrogen-incorporated arsenic-doped BaSi2

A comparative experimental and theoretical study of the role of H incorporation in As-doped BaSi2 films has been carried out based on the experimental results that an optimal time of H treatment for the increase in photoresponsivity and carrier lifetime was in the range of 1 ? 20 min. Adequate theoretical representation of the decay curves in the framework of the model for non-radiative processes accounted for various trap-related recombination mechanisms to estimate the trap concentration to be in the range of 1.9 ? 1013 to 1.7 ? 1014 cm-3. Additionally, the extended theoretical ab initio quantum-chemical simulation of the electronic structure of the studied systems was performed. It was revealed that interstitial As atoms can mostly provide trap states in the gap while H atoms neutralize such traps. The experimentally observed unexpected switching in conductivity from n-type to p-type and vice versa in As-doped BaSi2 with H incorporation was explained to specific configurations of point defects (an As impurity with a H atom in different positions and various interatomic As-H distances) which affect the position of states in the gap.