Fabrication of magnesium-doped gallium nitride nanorods and microphotoluminescence characteristicsKinetics of low-temperature activation of acceptors in magnesium-doped gallium nitride epilayers grown by metal-organic vapor-phase epitaxy Electrical characteristics of lateral p ϩ n diodes made from gallium nitride epitaxial layers on sapphire substrates are reported. The current-voltage characteristics are observed to have several distinct regions in which a tunneling current has been identified at low forward bias in addition to the conventional temperature-dependent diffusion current observed at moderate forward bias. A tunneling behavior indicates the presence of deep-level traps at the junction, which alter the electrical behavior of these junctions compared to the conventional behavior. In addition, space-charge-limited currents are found to influence these junctions at large forward and reverse bias.
Using site-specific plan-view transmission electron microscopy (TEM) and light emission imaging, we have identified stacking faults formed during forward biasing of 4H-SiC p-i-n diodes. These stacking faults (SFs) are bounded by Shockley partial dislocations and are formed by shear strain rather than by the condensation of vacancies or interstitials. Detailed analysis using TEM diffraction contrast experiments reveal SFs with leading carbon-core Shockley partial dislocations as well as with the silicon-core partial dislocations observed in plastic deformation of 4H-SiC at elevated temperatures. The leading Shockley partials are seen to relieve both tensile and compressive strain during p-i-n diode operation, suggesting the presence of a complex inhomogeneous strain field in the 4H-SiC layer.
Stacking-fault growth in SiC PiN diodes has been examined using light-emission imaging and stressing at 80 A/cm 2 and 160 A/cm 2 . Dark areas in the emission develop because of stacking faults and the current capability of the diode drops. More detailed images are produced by reducing the current by a factor of 1000. The low-current images are bright lines at dislocations bounding the stacking faults and at or near the stacking-fault intersection with the surface. Stacking faults nucleate 1-2 m below the surface. Most, but not all, continue growing until they span the diode. Growth dynamics and their dependence on the current density are discussed.
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