A new process is presented for fabricating enhanced-efficiency micro-pixelated vertical-structured light-emitting diode (µVLED) arrays based on ion-implantation technology. High-resistivity selective regions are locally introduced in the n-GaN layer by ion implantation and then used as effective and non-destructive electrical isolation for realizing µVLED arrays with ultra-small pixel diameters. The implantation energy-dependent and size-dependent opto-electrical characteristics of fluorine (F-) implanted µVLED arrays are investigated systematically. The results show that the optimally designed F- ion implantation not only can achieve smaller reverse leakage current but also can realize ion-induced thermal relaxation effectively and is more suited for fabricating high-resolution µVLED arrays with higher optical output power. For the F--implanted µVLED array with pixel diameters of 10 µm, a measured output power density reaches a value of 82.1 W cm−2 at a high injection current density of 220 A cm−2, before power saturation. Further, the output power densities and external quantum efficiencies of F--implanted µVLED arrays with pixel diameters less than 10µm show strong dependences on pixel size due to the presence of defects-related SRH process. So, the high-efficiency µVLED arrays with ultra-small pixel sizes could be fabricated by an appropriately designed ion implantation combined with control of defect densities to meet the industrial requirement of microdisplay applications.

Large-signal modulation capability, as an important performance indicator, is directly related to the high-speed optical communication technology involved. We experimentally and theoretically investigate the large-signal modulation characteristics of the simultaneous ground-state (GS) and the excited-state (ES) lasing in InAs/GaAs quantum dot laser diodes. The large-signal modulation capability of total light intensity in the transition regime from GS lasing to two-state lasing is unchanged as the bias-current increases. However, GS and ES large-signal eye diagrams show obvious variations during the transition. Relaxation oscillations and large-signal eye diagrams for GS, ES, and total light intensities are numerically simulated and analyzed in detail by using a rate-equation model. The findings show that a complementary relationship between the light intensities for GS and ES lasing exists in both the transition regime and the two-state lasing regime, leading to a much smaller overshooting power and a shorter settling time for the total light intensity. Therefore, the eye diagrams of GS or ES lasing are diffuse whereas those of total light intensity are constant as the bias-current increases in the transition regime.

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