Dislocations in GaN-Based Laser Diodes on Epitaxial Lateral Overgrown GaN Layers

Abstract

We have investigated dislocations in GaN-based laser diodes (LDs) on epitaxial lateral overgrown (ELO) GaN layers using transmission electron microscopy and cathodoluminescence microscopy and found a correlation between dislocations and device reliability. Dislocation density in the seed regions of ELO GaN layers is of the order of 10 8 cm --2 , while that in the wing regions is less than mid-10 6 cm --2 . The origin of dislocations in the wing regions is the extension of defects in highly defective regions near the GaN layer/substrate interface in the seed regions. The lifetime of LDs has a strong correlation with consumption power. However, some LDs have a shorter lifetime although their consumption power is almost the same. In the LDs with short lifetimes, dislocations lying in the c-plane were formed below the active regions, bent towards the c-axis and threaded upwards to active regions. These newly created dislocations can become detrimental to the device lifetime.

Process optimization for the effective reduction of threading dislocations in MOVPE grown GaN using in situ deposited masks

“…Using c-plane oriented sapphire ðAl 2 O 3 Þ, the large lattice mismatch between the GaN epitaxial layer and the applied substrate typically yields high dislocation densities up to 3 Â 10 9 cm À2 . Such crystal imperfections are known to affect the electrical and optical properties of GaN-based devices negatively, as they act as centers of nonradiative carrier recombination [1][2][3] and lead to degradation of LDs [4]. The in situ deposition of SiN x , acting as a nano-mask and influencing the morphology of the overgrown GaN layer, was found to be a fast and simple method leading to a defect reduction [5][6][7][8][9][10][11][12][13][14][15].…”

Aluminum incorporation in -layers and implications for growth optimization

“…Al x Ga 1Àx N layers are used as electron barriers in the active zone in light emitting structures, as cladding layers in lasers, and as barriers as well as quantum wells in UV light emitting diodes [1][2][3][4]. The quality of the layers is crucial to the performance of these devices.…”

Growth of AlxGa1−xN-layers on planar and patterned substrates

“…Al x Ga 1-x N-layers are used as electron barriers in the active zone in light-emitting structures, as cladding layers in lasers, and as barriers as well as quantum wells in UV light-emitting diodes [1][2][3]. The quality of the layers is crucial to the performance of these devices.…”