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Experiment and Simulation on Channel Mobility of In_0.53Ga_0.47As Quantum-well MOSFET Structures

• Authors: L. Yang, C. Cheng, M. T. Bulsara, E. A. Fitzgerald
• Sponsorship: SRC/FCRP MSD

This paper discusses a way to optimize the In_0.53Ga_0.47As quantum-well MOSFET structures from the prospective of channel mobility. We experimentally demonstrated that the barrier thickness and interfacial defect density are two key factors determining the channel mobility, while the effect of the oxide charge is negligible. The mobility model consisting of phonon scattering and coulomb scattering was applied to fit the experimental data. According to the model, for quantum-well MOSFET structures with in-situ ALD Al₂O₃, the mobility is dominated by coulomb scattering for the thin barrier case (<5 nm) and dominated by phonon scattering for the thick barrier case (>5 nm). At a barrier thickness of 4 nm, compared to a structure with in-situ ALD Al₂O₃ with the mobility of 6807 cm²/Vs, which corresponds to an interfacial charged defect density of 1.1×10¹³ cm^-2, the structure with in-situ CVD Al₂O₃ showed higher mobility (8883 cm²/Vs), which corresponds to a lower charged defect density (5×10¹² cm^-2).



Figure 1: Channel electron mobility versus the thickness of InGaAs/InAlAs barrier. The blue diamond symbols indicate the measured mobility. The magenta and red dots indicate the mobility limited by coulomb scattering and phonon scattering, respectively, and the black “+” symbols indicate the simulated final mobility.



Figure 2: Channel electron mobility versus the charged defect density. The blue diamond symbol and the green square symbol indicate the measured mobility for structure with CVD Al₂O₃/InGaAs interface and ALD Al₂O₃/InGaAs interface, respectively. The magenta and red dots indicate the mobility limited by coulomb scattering and phonon scattering, respectively, and the black “+” symbols indicate the simulated final mobility.