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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]