Experimental and computational analyses of electroabsorption in polar InGaN/GaN quantum zigzag heterostructures

Abstract

Traditional quantum confined Stark effect is well known to lead to strong electroabsorption in multiple quantum well (MQW) structures, yielding only red-shift of the absorption edge with the externally applied electric field, independent of the direction of the applied field. However, a little is known the electroabsorption behavior in III nitride quantum structures grown on c-plane of their wurtzite crystal structure, which is substantially different than the electroabsorption of conventional quantum structures. Such III-N heterostructures exhibit strong polarization fields and discontinuity of such polarization fields at their heterointerfaces causes stimulation of large electrostatic fields in alternating directions for their wells and barriers. Consequently, their energy band diagrams form a zigzag potential profile in conduction and valence bands, instead of those with square profiles. A natural and suitable approach for understanding these polarization fields and also developing insight to design related devices (e.g., electroabsorption modulators) is to study electroabsorption behavior as a function of the polarization field in such polar structures. To this end, we present a comparative, computational and experimental study of electroabsorption in our different designs of c-plane grown polar InGaN/GaN quantum structures with varying levels of polarization.