Micro-light-emitting diodes with III–nitride tunnel junction contacts grown by metalorganic chemical vapor deposition

Abstract

Micro-light-emitting diodes (µLEDs) with tunnel junction (TJ) contacts were grown entirely by metalorganic chemical vapor deposition. A LED structure was grown, treated with UV ozone and hydrofluoric acid, and reloaded into the reactor for TJ regrowth. The silicon doping level of the n ++ -GaN TJ was varied to examine its effect on voltage. µLEDs from 2.5 ' 10 %5 to 0.01 mm 2 in area were processed, and the voltage penalty of the TJ for the smallest µLED at 20 A/cm 2 was 0.60 V relative to that for a standard LED with indium tin oxide. The peak external quantum efficiency of the TJ LED was 34%.

Light Extraction Efficiency of GaN-Based Micro-Scale Light-Emitting Diodes Investigated Using Finite-Difference Time-Domain Simulation

“…To reach a high resolution in displays, μ-LEDs are required with dimensions below 20 μm. So far, μ-LEDs with dimensions even smaller than 10 μm have been demonstrated [7]- [11]. Several groups have investigated the effect of the chip dimension on the external quantum efficiency (EQE) of a μ-LED [6], [8]- [13].…”

Ge doped GaN and Al0.5Ga0.5N-based tunnel junctions on top of visible and UV light emitting diodes

“…Germanium n-doped GaN tunnel junctions on top of visible GaN LEDs were already demonstrated by Neugebauer et al 20 using an all-MOCVD growth approachnonetheless, this growth method is not optimal for tunnel junctions due to the re-passivation of the Mg acceptors by the H present in the growth chamber. A post-growth annealing to reactivate these acceptors would then be necessary, 21 but the p-doped layers in TJ devices are always buried under a highly n-doped layer, hindering the diffusion of H. [22][23][24] Additionally, for Ge-doped AlGaN layers, the Ge activation energy increases with the concentration of Al, 25 which yields a new challenge. Nonetheless, high electron concentrations (>1x10 20 cm -3 ) can be achieved with Ge-doped GaN 14 and AlGaN 25 layers by MBE.…”

GaN-based vertical-cavity surface-emitting lasers with tunnel junction contacts grown by metal-organic chemical vapor deposition

“…We believe that the BHF treatment improved the voltage by reducing Mg diffusion into the n ++ -GaN layer, which could compensate electron carriers required to form an abrupt junction. 15,19,21) Finally, the best results were obtained from the sample treated in BHF with in-situ activation prior to TJ regrowth, which showed voltages of 3.4 V at 20 A=cm 2 and 4.5 V at 1 kA=cm 2 . These J-V characteristics are reasonably close to those of a diode with the MOCVD-MBE hybrid TJ contacts reported by Young et al (3.05 V at 20 A=cm 2 ), 15) but the voltage of the MOCVD TJ sample could be increased owing to structural differences, including poor n-contact on lightly doped n-GaN and extra resistance from the substrate.…”