First-principles simulation of Sb-based superlattice for infrared detection with an <i>ad hoc</i> functional

The 6.1 Å family III–V semiconductors are promising for infrared detection due to the flexibility in wavelength tuning as well as the excellent technical compatibility. Theoretical design of type-II superlattices based on e.g., InAs and GaSb has been carried out mainly through empirical tight binding or the k⋅p method. First-principles density functional theory calculation, on the contrary, suffers from bandgap inaccuracy problems. Recently, the shell DFT-1/2 method has been applied to InAs/GaSb superlattice calculations, demonstrating great application potential, but it has no adjustable parameter to reach the stringent accuracy required by the industry. In this work, we reveal the origin of the bandgap inaccuracy and propose two approaches that can be combined to yield accurate electronics structures for these superlattices, typically within 2% from the experimental bandgap. An ad hoc functional of the generalized gradient approximation flavor is used to better describe the lattice parameters of these III–V semiconductors. Moreover, a shell DFT + A–1/2 method is proposed to allow for physically reasonable parameters, which can be tuned to fit the electronics structure to experimental. Calculation results for a series of InAs/GaSb superlattices are analyzed, with comparison to experiments.