Transport dynamics of photo-induced carriers in GaN quantum well infrared photodetectors influenced by triangular...

The intrinsic spontaneous and piezoelectric polarizations of GaN lead to the formation of triangular wells and barriers, resulting in the manifestation of chaotic transport models in GaN quantum well intersubband transition (ISBT) infrared detectors and giving rise to various adverse effects. The APSYS software was utilized to construct a novel GaN quantum well ISBT infrared detector in this study. By endeavoring to modify the quantum well structure, our objective was to precisely adjust the energy level of the first excited state (E1) to align with the apex of the triangular barrier. The objective is to reduce the transport barrier for photo-induced carriers and simultaneously investigate the mechanisms through which the triangular potentials influence the transport modes of ISBT infrared detectors. The construction of a GaN/AlGaN quantum well device reveals that the inclusion of 10 periods of 1.7/2.0 nm GaN/Al_0.8Ga_0.2N in the device structure results in an ISBT absorption wavelength of approximately 1550 nm. In comparison to the deep well structure featuring 2.0/2.0 nm GaN/AlN, the polarization field strengths of both wells and barriers in the quantum well region exhibit a reduction of 23% and 36%, respectively, while the depth of the well decreases by 0.35 eV. The E1 energy level penetrates the region of a triangular barrier, resulting in an approximate 18.5-fold enhancement of the absorption coefficient. By employing innovative transient spectroscopy techniques in conjunction with AC impedance spectroscopy, we have conducted an in-depth analysis of the transport dynamics of photo-induced carriers. The results reveal that the time constant for carrier transport within the E1 energy level, situated in the region of a triangular barrier, amounts to 318.9 ps, thereby indicating a remarkable enhancement in the overall transport process. Furthermore, based on impedance spectroscopy data, this work has successfully derived equivalent circuit models for various quantum well structures and distinct carrier transport pathways, thus providing valuable theoretical insights to optimize photo-induced carrier transportation.