Optical gain characteristics of a-plane GaN/AlGaN quantum well lasers grown on strain-engineered MgZnO layer

Abstract

Optical gain characteristics of a-plane (11 2¯ 0) AlGaN/GaN quantum well (QW) lasers grown on a GaN buffer with strain anisotropy using a strain-engineered MgZnO layer were investigated using the multiband effective mass theory. The calculated transition energies for QW structures grown on MgZnO layer are in good agreement with experimental results. The optical gain of the QW structure grown on the MgZnO substrate is dominated by the z′-polarization because the dominant states constituting the topmost valence subband for the QW structure changes from |Y′>−to|Z′>-like and carriers occupy higher states above k∥=0 at a higher carrier density. On the other hand, the optical gain of the QW structure grown on conventional GaN buffer is dominated by both y′- and z′-polarizations. Thus, the optical polarization characteristics of a-plane AlGaN/GaN QW lasers can be engineered by using MgZnO substrate.