Droop-Free, Reliable, and High-Power InGaN/GaN Nanowire Light-Emitting Diodes for Monolithic Metal-Optoelectronics

Abstract

A droop-free nitride light-emitting diode (LED) with the capacity to operate beyond the "green gap" has been a subject of intense scientific and engineering interest. While several properties of nanowires on silicon make them promising for use in LED development, the high aspect ratio of individual nanowires and their laterally discontinuous features limit phonon transport and device performance. Here, we report on the monolithic integration of metal heat-sink and droop-free InGaN/GaN quantum-disks-in-nanowire LEDs emitting at ∼710 nm. The reliable operation of our uncooled nanowire-LEDs (NW-LEDs) epitaxially grown on molybdenum was evident in the constant-current soft burn-in performed on a 380 μm × 380 μm LED. The square LED sustained 600 mA electrical stress over an 8 h period, providing stable light output at maturity without catastrophic failure. The absence of carrier and phonon transport barriers in NW-LEDs was further inferred from current-dependent Raman measurements (up to 700 mA), which revealed the low self-heating. The radiative recombination rates of NW-LEDs between room temperature and 40 °C was not limited by Shockley-Read-Hall recombination, Auger recombination, or carrier leakage mechanisms, thus realizing droop-free operation. The discovery of reliable, droop-free devices constitutes significant progress toward the development of nanowires for practical applications. Our monolithic approach realized a high-performance device that will revolutionize the way high power, low-junction-temperature LED lamps are manufactured for solid-state lighting and for applications in high-temperature harsh environment.

Thermodynamic photoinduced disorder in AlGaN nanowires

“…79 This model, which has widely been used to describe the dynamics of heavily disordered systems, 80,81 provides a direct measurement of the effects of high excitation carrier density and disorder within the material, 82 such as compositional variation in nanowires. 34 As can be seen in Fig. 6, β between 0.63 and 0.65 at temperatures above 100 K, indicating a behavior that was nearly independent of T, therefore confirming the low compositional disorder within the measured Al 0.18 Ga 0.82 N nanowires.…”

“…29 GaN-based nanowires have recently emerged as the center of attention as potential building blocks for future nanostructured long-term stable opto-electrothermal devices. [30][31][32] Even though GaN nanowire-based devices, including tunnel-injected DUV light-emitting diodes (LEDs) 33 and LEDs for monolithic metal-optoelectronics 34 and high-power light emitters, 35 have recently been realized, understanding and optimizing the electrothermal characteristics 36,37 of GaN-based nanowires is critical for identifying and achieving their full potential in opto-electrothermal device applications. 38,39 As a consequence of the thermal activation of non-radiative recombination channels, we observed an increasing trend in the amount of generated photoinduced entropy of the InGaN nanowire system as its temperature approached room temperature, which is a valid assessment of the thermodynamic disorder in photoluminescent semiconducting materials.…”

Evaluation of Light Extraction Efficiency of GaN-Based Nanorod Light-Emitting Diodes by Averaging over Source Positions and Polarizations

“…Recently, a GaN-based nanorod LED structure has drawn increasing attention as an alternative technology to overcome the efficiency limitation of current LED structures [13][14][15][16]. Nanorod structures have high potential to enhance the efficiency of LEDs significantly.…”

Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy

“…Moreover, their optical qualities seem to be not compromised, e.g., InN and GaN nanowires grown on silicon oxide show similar photoluminescence characteristics compared to the nanowires grown on Si [99]. Recently, visible and UV LEDs with InGaN and AlGaN quantum wells/quantum disks have been demonstrated on metal substrates [102][103][104][105][106]. III-nitride nanowire structures on graphene have also been investigated.…”