Temperature effect on charge-state transition levels of defects in semiconductors

作者：Qiao, Shuang; Wu, Yu-Ning; Yan, Xiaolan; Monserrat, Bartomeu; Wei, Su-Huai; Huang, Bing^*

来源：Physical Review B, 2022, 105(11): 115201.

DOI：10.1103/PhysRevB.105.115201

• INITIO MOLECULAR-DYNAMICS
• TOTAL-ENERGY CALCULATIONS
• 1ST-PRINCIPLES CALCULATIONS
• PHASE-TRANSITION
• EFFICIENCY
• METALS
• GAP

Defects are crucial in determining the overall physical properties of semiconductors. Generally, the charge-state transition level epsilon(alpha)(q/q'), one of the key physical quantities that determines the dopability of defects in semiconductors, is temperature dependent. However, little is known about the temperature dependence of epsilon(alpha)(q/q' ) and, as a result, almost all existing defect theories in semiconductors are built on a temperature-independent approximation. In this paper, by deriving the basic formulas for temperature-dependent epsilon(alpha)(q/q' ), we have established two fundamental rules for the temperature dependence of epsilon(alpha)(q/q') in semiconductors. Based on these rules, surprisingly, it is found that the temperature dependencies of epsilon(alpha)(q/q') for different defects are rather diverse: it can become shallower, deeper, or stay unchanged. This defect-specific behavior is mainly determined by the synergistic or opposing effects between free-energy corrections (determined by the local volume change around the defect during a charge-state transition) and band-edge changes (which differ for different semiconductors). These basic formulas and rules, confirmed by a large number of state-of-the-art temperature-dependent defect calculations in GaN, may potentially be widely adopted as guidelines for understanding or optimizing doping behaviors in semiconductors at finite temperatures.