Giant spontaneous polarization in zinc-blende III-V semiconductors

The discovery of ferroelectricity in wurtzite nitrides has paved the way for measuring and understanding spontaneous polarization in III-V semiconductors. However, the calculation of polarization effects at heterointerfaces, crucial for numerous electronic and photonic applications, remains a topic of debate. The need for a reference structure to calculate spontaneous polarization has led to discussions over whether to use the zinc-blende or layered hexagonal structures as the reference for wurtzite crystals. In this Letter, we argue that the layered hexagonal structure is not only a better reference due to its vanishing formal polarization, but also the appropriate choice for the wurtzite system to reproduce the polarization values observed in ferroelectric switching experiments. This leads to the idea of using ferroelectricity as a basis for defining spontaneous polarization. Applying this definition, we extend our analysis to III-V zinc-blende semiconductors and reveal that they can exhibit a spontaneous polarization approximately three times larger than that of wurtzite, thereby refuting the longstanding assumption that it is zero. Through this example, we illustrate that spontaneous polarization is not inherently linked to charge density at interfaces.