Defects in degraded GaN-based laser diodes

Abstract

We investigate degraded GaN‐based laser diodes (LDs) fabricated on epitaxial lateral overgrown (ELO) GaN layers using transmission electron microscopy. The dislocation density in the wing region of the ELO is of the order of 106/cm2 and there are approximately ten threading dislocations in the laser stripe. Neither dislocation multiplication from the threading dislocations nor any structural changes of the threading dislocations were observed in the devices, which were degraded within approximately one hundred hours under 30 mW continuous operation at 25 °C. We can, therefore, conclude that degradation in GaN‐based LDs is not responsible for the recombination enhanced dislocation motion that is usually observed in zincblende structure‐based LDs. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low-frequency noise in as-fabricated and degraded blue InGaAs/GaN LEDs

“…It has been noted in most reports that optical power degradation of InGaN/GaN LEDs has the same nature as that in lasers and is accompanied by the gen eration of defects under the action of the injection cur rent, the electromigration of metal ions from contact pads, and a rise in the density of states at heterointer faces [5,[7][8][9][10]. However, it is still unclear how optical power degradation is related to changes in the proper ties of the defect system [5,7,10].…”

Effects of Mg dopant on the degradation of InGaN multiple quantum wells in AlInGaN-based light emitting devices

“…Although a few groups reported the possible degradation mechanism of the AlInGaN-based LD/LEDs [8][9][10][11][12][15][16][17], it has not been fully understood yet. We proposed the degradation possibility of Mg dopant diffusion into the InGaN active layer by applied voltage [15].…”

“…Additional issue is the high dislocation density in GaN epilayer due to the large lattice mismatch between GaNbased material and sapphire substrate [9]. However, the degradation of GaN-based LD/LEDs is not responsible for the multiplications of the dislocation motions that is usually observed in zincblende structure-based LDs [10]. From the dependence on dislocation density of life time of GaNbased LDs, it has been believed that one of degradation mechanisms is the dislocation-related diffusion process [11,12].…”

Photonic Devices

“…Thus lasers with COD levels of 250 mW can be fabricated using GaN-based materials without the need for window structures. Further, TEM observations of structures after failure show there to be no increase in the dislocation density, although such increases are found in GaAs-based lasers [224]. As shown, a ripple pattern is observed in the in the θ ⊥ direction for lasers grown on sapphire substrates due to optical interference at the sapphire/GaN interface.…”