In-situ neutron-transmutation for substitutional doping in 2D layered indium selenide based phototransistor

Neutron-transmutation doping (NTD) has been demonstrated for the first time in this work for substitutional introduction of tin (Sn) shallow donors into two-dimensional (2D) layered indium selenide (InSe) to manipulate electron transfer and charge carrier dynamics. Multidisciplinary study including density functional theory, transient optical absorption, and FET devices have been carried out to reveal that the field effect electron mobility of the fabricated phototransistor is increased 100-fold due to the smaller electron effective mass and longer electron life time in the Sn-doped InSe. The responsivity of the Sn-doped InSe based phototransistor is accordingly enhanced by about 50 times, being as high as 397 A/W. The results show that NTD is a highly effective and controllable doping method, possessing good compatibility with the semiconductor manufacturing process, even after device fabrication, and can be carried out without introducing any contamination, which is radically different from traditional doping methods.