Density of defect states retrieved from the hysteretic gate transfer characteristics of monolayer MoS2 field effect transistors

Defect states play an important role in low-dimensional semiconductor devices. However, it becomes increasingly challenging to find the density of defect states for ultra-scaled devices using traditional capacitive techniques such as capacitance-voltage (CV) method and deep level transient spectroscopy (DLTS). Here, we proposed a model to quantitatively retrieve the density of defect states from the hysteretic gate transfer characteristics of field effect transistors (FETs), and applied it to monolayer MoS2 FETs before and after superacid treatment. We found that the superacid treatment significantly reduced the density of deep level defects. As a result, the photoluminescence was enhanced 19 folds due to the suppression of non-radiative recombination via deep level defects.