Absorption of terahertz radiations in two-dimensional semiconductors

Nonlinear free-carrier absorption of terahertz radiations in semiconductor heterojunctions have theoretically been investigated by considering multiple photon process and conduction-valence interband impact ionisation (II). We have determined the field and frequency dependent absorption rate. It is found that electron-disorder scatterings are important at low to intermediate fields, and the high field absorption is dominated by II processes.