Comprehensive study of components affecting extrinsic transconductance in In_0.7Ga_0.3As quantum-well high-electron-mobility transistors for image sensor applications

The components affecting the extrinsic transconductance (g_{m_ext}) in In_0.7Ga_0.3As quantum-well (QW) high-electron-mobility transistors (HEMTs) on an InP substrate were investigated. First, comprehensive modeling, which only requires physical parameters, was used to explain both the intrinsic transconductance (g_{m_int}) and the _{gm_ext} of the devices. Two types of In_0.7Ga_0.3As QW HEMT were fabricated with gate lengths ranging from 10 μm to sub-100 nm. These measured results were correlated with the modeling to describe the device behavior using analytical expressions. To study the effects of the components affecting g_{m_int}, the proposed approach was extended to projection by changing the values of physical parameters, such as series resistances (R_S and R_D), apparent mobility (μ_{n_app}), and saturation velocity (v_sat).