Abstract
The energy positions and wave function shapes of the ground and excited states of impurities, including resonance states, are studied using the expansion of the impurity wave function in basis functions. The structures under study are rectangular GaAs/AlGaAs quantum wells with four different widths. In all cases, the impurity binding energy (relative to the corresponding sub-band) has a maximum at or near the center of the quantum well, decreases as the heterointerface is approached, and apparently has a limit of 0 if the impurity moves deeper into the barrier. If the impurity moves away from the center of the quantum well, then the "center of mass" of the electron charge of non-resonant impurity states follows the impurity atom, and the "center of mass" of the electron charge of the resonant impurity states moves away from it. The effect is more pronounced for the ground and first resonance states for wider quantum wells, and the shifts reach a maximum when the impurity atom is positioned near the midpoint of the path between the quantum well center and the heterointerface.
Keywords:
expansion method; hydrogenic impurity states; semiconductor heterostructures.
Grants and funding
VA: CAD and ALM worked within the Project 2022-52190 “Nanoestructuras semiconductoras con simetría axial basadas en InAs y GaAs para aplicaciones en electrónica ultra e híper rápida” 2710—Programática 2021–2022: Ciencias Exactas y Naturales of the University of Antioquia co-financed by the University of Medellin Ref. 1323. CAD and ALM are grateful to Colombian agencies CODI Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia and projects “Propiedades magneto-ópticas y óptica no lineal en superredes de Grafeno”, “Estudio de propiedades ópticas en sistemas semiconductores de dimensiones nanoscópicas”, “Propiedades de transporte, espintrónicas y térmicas en el sistema molecular ZincPorfirina”, “Complejos excitónicos y propiedades de transporte en sistemas nanométricos de semiconductores con simetría axial”, and ”Nanoestructuras semiconductoras con simetría axial basadas en InAs y GaAs para aplicaciones en electrónica ultra e híper rápida”) and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD and ALM exclusive dedication projects 2023–2024). MEMR acknowledges support form Mexican CONAHCYT through Grant A1-S-8218This research received no external funding. D.L. acknowledges partial financial support from Centers of Excellence with BASAL/ANID, Chile Financing, AFB220001, CEDENNA.