Piezoelectric tunability and topological insulator transition in a GaN/InN/GaN quantum-well device

Abstract Using an 8-band <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mtext mathvariant="bold">k</mml:mtext> </mml:mrow> </mml:mrow> <mml:mo>⋅</mml:mo> <mml:mrow> <mml:mrow> <mml:mtext mathvariant="bold">p</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> model it is demonstrated through the combination of strain and piezoelectricity that increasing the InN quantum-well thickness of a GaN-InN-GaN device changes the InN material from a positive bandgap semiconductor to a topological insulator (negative bandgap). Moderate strain tuning of a four monolayer InN layer for a GaN-InN-GaN device reveals a giant (one order of magnitude) tuning of current–voltage characteristics. It is verified that piezoelectricity plays an important role in controlling electron transport through the InN layer.