Probing dopants in wide semiconductor quantum point contacts.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Electronics

Background:

• Semiconductor quantum point contacts (QPCs) are crucial for understanding electron transport.
• The impact of random impurities on QPC properties is not fully understood.
• Realistic device designs require consideration of impurity effects.

Purpose of the Study:

• To simulate the effects of randomly distributed impurities on QPC conductance, spin polarization, and electron localization.
• To investigate how impurity proximity to the 2DEG influences transport phenomena.
• To guide the design of high-mobility semiconductor devices by evaluating impurity nature.

Main Methods:

• Numerical simulations using density functional theory (DFT) in the local spin-density approximation (LSDA).
• Modeling of gated semiconductor QPCs with realistic impurity distributions.
• Calculation of conductance as a function of gate voltage for various impurity scenarios.

Main Results:

• When impurities are far from the 2DEG, conventional ballistic transport occurs.
• Impurities near the 2DEG induce electron localization, conductance fluctuations, and resonances.
• Resonances shift and decrease in amplitude with asymmetrically charged gates, while interaction effects remain.
• Spin polarization can manifest as stripes in wide QPCs.

Conclusions:

• The position and ionization state of random impurities significantly impact QPC electronic properties.
• Electron localization and conductance anomalies are direct consequences of nearby impurities.
• Understanding these impurity effects is vital for optimizing high-mobility device performance.