An AC-based GaN blue light-emitting diodes (LEDs) with different designs (series and Wheatstone Bridge configurations) were successfully fabricated and demonstrated at wafer and chip level under CSIR network (R-Nano) programme. In the first design, 42 micro-LED chips were connected in a series for a high voltage operation, where the size of each chip was ~ 250 μm x 220 μm leading to the total size of integrated monolithic blue LED chip as ~ 2.4 mm x 1.8 mm. Fig. 19 shows the fabricated ACLED chip after dicing. In the second design, micro- LED chips were connected in Wheatstone bridge configuration in order to increase the emission area. Figs. 19 & 20 show fabricated AC-LED chips in a series (with 42 microchips) and Wheatstone bridge configuration (with 6 microchips), respectively.
Fig.19: Fabricated GaN AC-LED chip (series configuration) after dicing
Fig. 20: Fabricated AC-LED chip (wheatstone bridge configuration) after dicing
Fig. 21: I-V characteristics of fabricated AC-LED chip (series configuration: 42 microchips) under AC source
Fig. 22: I-V characteristics of fabricated AC-LED chip (Wheatstone bridge configuration: 6 micro-chips) under AC source
Threshold voltages of ~ 105 V for AC-LED chips connected in the series and 11.5 V for Wheatstone bridge configuration have been achieved. Figs. 21 & 22 show the current-voltage (I-V) characteristics of AC-LED chips under AC source. Packaging and further performance analyses are in progress.