Direct lift-off and the piezo-phototronic study of InGaN/GaN heterostructure membrane.

Abstract Internal polarizations, caused by the intrinsic material properties and lattice mismatch during material epitaxial growth, exist inherently in III-nitrides and limit significantly their practical applications. Here, InGaN/GaN single quantum well (SQW) structure grown on sapphire substrate was directly exfoliated by electrochemical (EC) etching. The separated InGaN/GaN SQW heterostructure membranes (SQW-HMs) exhibit substantial relaxation of internal strain and polarization compared to the as-grown samples. To further modulate/tune the internal polarizations and corresponding opto-electronic properties of the SQW-HMs, the piezo-phototronic effect was introduced by applying external stress on the freestanding membrane under ultraviolet (UV) light illumination. The obtained photoluminescence (PL) intensity can be effectively modulated in different manners under tensile and compressive straining conditions. Energy diagrams of the SQW-HMs under free and straining conditions were carefully analyzed to illustrate the working mechanisms of the piezo-phototronic modulations. This research provides a new approach to optimize the performances of III-nitride devices and expand their further applications in optical communications and optical integration systems. Graphical abstract In this work, the piezo-phototronic effect is introduced to modulate the optical properties of the freestanding InGaN/GaN heterostructure membrane, the corresponding physical mechanisms are systematically analyzed. Image 1 Highlights • Electrochemical (EC) etching is utilized for direct fabrication of the freestanding InGaN/GaN single-quantum-well heterostructured membrane (SQW-HM). • The optical properties of the released HM, compared with the as-grown InGaN/GaN film, are obviously optimized due to the relaxation of intrinsic stress. • The piezo-phototronic effect study of the released SQW-HM is systematically performed and the corresponding mechanisms are illustrated by analyzing the energy diagrams. [ABSTRACT FROM AUTHOR]