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

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 [1]. However, a little is known the electroabsorption behavior in IIInitride 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 [2]. 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 [3, 4]. 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.