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Light‐emitting diode (LED) arrays fabricated on a polycrystalline metal substrate are demonstrated using a novel technique that enables the growth of epitaxial metal‐organic chemical vapor deposition (MOCVD) GaN layers on non‐single‐crystal substrates. Epitaxial GaN is deposited directly on metal foil using an intermediate ion beam‐assisted deposition (IBAD) aligned layer. For a single 170 μm‐diameter LED on the metal foil, electroluminescence (EL) spectrum shows a peak wavelength of ≈452 nm and a full width at half maximum (FWHM) of ≈24 nm. The current–voltage (I–V) characteristics show a turn‐on voltage of 3.7 V, a series resistance of 10 Ω. LEDs on metal show a relative external quantum efficiency (EQE) that is roughly 3× lower than that of similar LEDs fabricated on a sapphire substrate. InGaN LEDs on large‐area non‐single‐crystal substrates such as metal foils enable large‐area manufacturing, reducing production cost, and opening the door for new applications in lighting and displays. [ABSTRACT FROM AUTHOR]

Impacts of silicon, carbon, and oxygen interfacial impurities on the performance of high‐voltage vertical GaN‐based p–n diodes are investigated. The results indicate that moderate levels (≈5 × 1017 cm−3) of all interfacial impurities lead to reverse blocking voltages (Vb) greater than 200 V at 1 μA cm−2 and forward leakage of less than 1 nA cm−2 at 1.7 V. At higher interfacial impurity levels, the performance of the diodes becomes compromised. Herein, it is concluded that each impurity has a different effect on the device performance. For example, a high carbon spike at the junction correlates with high off‐state leakage current in forward bias (≈100× higher forward leakage current compared with a reference diode), whereas the reverse bias behavior is not severely affected (> 200 V at 1 μA cm−2). High silicon and oxygen spikes at the junction strongly affect the reverse leakage currents (≈ 1–10 V at 1 μA cm−2). Regrown diodes with impurity (silicon, oxygen, and carbon) levels below 5 × 1017 cm−3 show comparable forward and reverse results with the reference continuously grown diodes. The effect of the regrowth interface position relative to the metallurgical junction on the diode performance is also discussed. [ABSTRACT FROM AUTHOR]

Replacing a portion of the upper III-nitride cladding with indium-tin-oxide (ITO) has several potential advantages for GaN-based laser diodes (LDs). For green LDs, use of ITO in the waveguide structure reduces the epitaxial p-cladding thickness and growth time, which in turn may reduce thermal damage to the active region. We design ITO-clad blue and green semipolar [formula] LDs using asymmetric InGaN waveguiding layers to center the mode on the active region. Lasing is demonstrated at 471 nm with threshold current density of 6.2 kA/cm2 for a device with 200 nm p-GaN and at 518 nm for a device with only 300 nm of p-GaN. [ABSTRACT FROM AUTHOR]

Abstract: Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150lmW−1, and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as incandescent and compact fluorescent (CFL) lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. The emphasis on nonpolar and semipolar LEDs highlights high-power violet and blue emitters, and we consider the effects of indium incorporation and well width. Semipolar GaN materials have enabled the development of high-efficiency LEDs in the blue region and recent achievements of green laser diodes at 520nm. [Copyright &y& Elsevier]

We demonstrate an electrically injected semipolar [formula] laser diode (LD) grown on an intentionally stress relaxed n-In0.09Ga0.91N waveguiding layer. Detrimental effects of misfit dislocations (MDs) in the proximity of the active region were effectively suppressed by utilizing a p/n-Al0.2Ga0.8N electron/hole blocking layer between the dislocated heterointerfaces and the active region. The threshold current density of the LD was ∼20.3 kA/cm2 with a lasing wavelength of 444.9 nm. This LD demonstrates an alternative approach in semipolar AlInGaN LD waveguide design where the thickness and composition of the waveguiding and/or cladding layers are not limited by the critical thickness for MD formation. [ABSTRACT FROM AUTHOR]