Dynamical Behavior of a Stacked Blue Laser Diode Consisting of Two Active Regions with Wide InGaN Quantum Wells and Two Tunnel Junctions

In nitride-based laser diodes, the poor conductivity of the p-type region, higher light absorption, and the difficult processing of an ohmic p-contact with low resistance are major challenges. Recently interband tunnel junctions (TJs) have been used to replace much of the hole transport layers by electron transport layers, and also to allow for two n-type contacts. In this work, GaN-based laser diode stacks with TJs are analyzed. The devices are grown with plasma-assisted molecular beam epitaxy and include two waveguides with active regions consisting of 25 nm wide InGaN quantum well (QW), each, which are connected through a TJ. A second TJ is placed on top to eliminate the p-type contact. In this study, the time-dependent spectral behavior of such structures is analyzed by streak camera measurements. The two QWs have different lasing thresholds and emission wavelength. Using the temporal resolution of the streak camera, a lasing onset of the second QW a few nanoseconds after the first one is observed. Single shot measurements show unusual intensity oscillations from both QWs, however, one is stable and the other laser diode (LD) has irregular oscillations. Single shot measurements on a stack of two laser diodes (LDs) connected by a tunnel junction (TJ) show that the emission of both quantum wells (QWs) exhibits fast oscillations. The dynamics of the two QWs differ. The oscillations of the second QW are stable, while the oscillations of the first disappear in integrated measurements because they are temporally unstable.image (c) 2024 WILEY-VCH GmbH