Intersubband absorption coefficients of GaN/AlN and strain-compensated InGaN/InAlN quantum well structures

Intersubband (ISB) transition absorption properties of strain-compensated InGaN/InAlN quantum well (QW) structures grown on GaN substrate were investigated using an effective mass theory. The interband dipole moment of the strain-compensated InGaN/InAlN QW structure is shown to be comparable to that of the conventional GaN/AlN QW structure. However, the strain-compensated InGaN/InAlN QW structure shows much larger intersubband absorption coefficient than the conventional GaN/AlN QW structure. This is mainly due to the fact that the former shows much larger quasi-Fermi-level separation than the latter because the electron effective mass is reduced with the inclusion of Indium. As a result, the strain-compensated QW structures could be used as ISB photodetectors for telecommunication operating at 1.55 μm with a higher absorption coefficient and a reduced strain, compared to conventional GaN/AlN QW structures.