Metalorganic chemical vapor deposition-grown tunnel junctions for low forward voltage InGaN light-emitting diodes: epitaxy optimization and light extraction simulation

Abstract In this work, we demonstrate the detailed optimization of metalorganic chemical vapor deposition (MOCVD)-grown tunnel junctions (TJs) utilizing selective area growth (SAG) for regular size (0.1 mm 2 ) and micro-size InGaN light-emitting diodes (LEDs and µ LEDs). Finite-difference time-domain simulations show that the SAG apertures result in a more directional light emission of far-field radiation pattern for the SAG TJ LEDs grown on patterned sapphire substrate. Moreover, it is noted that the n-InGaN insertion layer and Si-doped concentration in the n + GaN TJs layer is essential to realize a low forward voltage ( V f ) in TJs LEDs. For both 0.1 mm 2 LEDs and µ LEDs, the V f is independent on the SAG aperture space varied from 3 to 8 µ m when the Si-doping level in the n + GaN layer is as high as 1.7 × 10 20 cm −3 . The optimized TJ LEDs exhibit a comparable differential resistance of 1.0 × 10 −2 Ω cm 2 at 100 A cm −2 and a very small voltage penalty of 0.2–0.3 V compared to the conventional indium tin oxide contact LEDs. The low V f penalty is caused by a higher turn on voltage, which is the smallest one among the MOCVD-grown TJs LEDs and comparable to the best molecular beam epitaxy-grown TJs LEDs.