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We report the effect of V-shaped pit size, inverted hexagonal pits embedded in InGaN multiple quantum well, on the reverse leakage current of InGaN light-emitting diodes (LEDs). It was found that the reverse leakage current of InGaN LEDs with larger V-shaped pits is significantly reduced from 1.80 mA down to 3.84 nA at -30~V by several orders of magnitude. We claim that this improvement is accounted for increased Poole-Frenkel barrier height of carrier trapped at the deep centers via enlarged V-pit formation, consequently resulting in lower reverse current of InGaN LEDs. [ABSTRACT FROM AUTHOR]

We investigate the reverse leakage characteristics of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrate by metal–organic chemical vapor deposition. The reverse leakage characteristics of InGaN/GaN LED on silicon are measured as low as \sim10 nA at -5 V and -10 \mu\A at -15 V. Temperature-dependent current–voltage ( I–V) measurements of LED devices reveal that the reverse leakage current mechanism is mainly attributed to the field-enhanced thermionic emission, also known as Poole–Frenkel emission, of carriers from deep centers within the space charge region up to \sim-18 V. The analysis of T–I –V curve yields the calculation of the coefficient of the Poole–Frenkel effect (\1.12 \times \10^-4\ \eV\cdot \V^-1/2\cdot\cm^1/2) and activation energies of carriers ( \sim214 meV at -5 V). With further increase of reverse bias, up to - 40 V, LED devices exhibit the onset of space-charge-limited leakage current mechanism without any local breakdown. [ABSTRACT FROM AUTHOR]

We report the characteristics of forward tunneling current in InGaN/GaN multiple quantum well light-emitting diodes (LEDs) grown on Si (111) substrate. Temperature-variable current-voltage (I-V) measurement from 80 K to 400 K reveals that forward current regimes can be distinguished by corresponding slopes in semi-logarithmic plot, which are associated with different forward conduction mechanisms of InGaN LED. Temperature-insensitive tunneling behavior appears to be dominant at low current injection regime for InGaN LEDs on Si. Conductive atomic force microscopy analysis indicates that V-pits associated with threading dislocations could be main leakage path of forward tunneling current of InGaN LED on Si. [ABSTRACT FROM AUTHOR]

A GaN-based vertical-cavity surface-emitting laser (VCSEL) has been demonstrated in an extended cavity structure. A VCSEL device had a long extended cavity, which consisted of a sapphire substrate as well as a GaN epilayer and had an integrated microlens on one side. High-reflection dielectric mirrors were deposited on both sides of the laser cavity. The laser was optically pumped and operated at room temperature. The VCSEL device lased at a low threshold excitation intensity of 160 kW/cm[sup 2]. In contrast to a conventional microcavity-VCSEL structure, the VCSEL operated in multiple longitudinal modes with mode spacing consistent with its physical thickness. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]