Strained M-plane GaN for polarization-sensitive applications

The realization of polarization-sensitive photodetectors based on strained M-plane GaN is reported. The strain-induced band-structure modification is revisited, emphasizing the effect of anisotropic strain on the optical selection rules. Results show that the polarization sensitivity of these devices in the range of 10 nm can be tuned in the vicinity of the GaN band edge by using films under different strain states. The photodetector characteristics, such as the specific detectivity or the contrast between the detected light polarized perpendicular and parallel to the c-axis and design guidelines to fabricate this particular type of devices, will also be presented. In contrast to conventional semiconductor photodetectors, it is shown that the film thickness dramatically affects the main parameters of these novel devices, namely through the dependence of the valence band splitting and linear dichroism on strain.