Strained In_x Ga_{(1-x )}As/InP near surface quantum wells and MOSFETs

We present electronic band structure properties of strained InxGa(1-x)As/InP heterostructure near surface quantum wells oriented in the (100) crystallographic direction using eight-band k · p theory, which are further parameterized by an energy level, effective mass, and nonparabolicity factor. The electronic band structure parameters are studied for the well composition of 0.2 ≤ x ≤ 1 and thickness from 5 to 13 nm. The bandgap and effective mass of the strained wells are increased for x >0.53 due to compression strain and decreased for x < 0.53 due to tensile strain as compared to that of unstrained wells. The calculated band structure parameters are utilized in modeling long channel In0.71Ga0.29As/InP quantum well MOSFETs, and the model is validated against measured I-V and low frequency C-V characteristics at room temperature and cryogenic temperature. Exponential band tails and first- and second-order variation of the charge centroid capacitance and interface trap density are included in the electrostatic model. The Urbach parameter obtained in the model is E0 = 9 meV, which gives subthreshold swing (SS) of 18 mV/dec at T = 13 K and agrees with the measured SS of 19 mV/dec. Interface trap density is approximately three orders higher at T = 300 K compared to T = 13 K due to multi-phonon activated traps. This model emphasizes the importance of considering disorders in the system in developing device simulators for cryogenic applications.