Strain-compensated AlGaN∕GaN∕InGaN cladding layers in homoepitaxial nitride devices

Abstract

One of the most important problems in III-nitride violet laser diode technology is the lattice mismatch between the AlGaN cladding layers and the rest of the epitaxial structure. For efficiently working devices, it is necessary to have both a high Al content and thick claddings. This leads, however, to severe sample bowing and even cracking of the upper layer. In this work, we propose a cladding structure of strain-compensated AlGaN∕GaN∕InGaN superlattice grown by metal-organic vapor phase epitaxy on bulk GaN substrates. Various thicknesses and compositions of the layers were employed. We measured the radius of bowing, lattice mismatches, aluminum and indium contents, and densities of threading dislocations. The proposed cladding structures suppress bowing and cracking, which are the two parasitic effects commonly experienced in laser diodes with bulk AlGaN claddings. The suppression of cracking and bowing is shown to occur due to modified strain energy distribution of the superlattices structure.

InGaN/AlGaN stress compensated superlattices coherently grown on semipolar () GaN substrates

“…One possible application of InGaN/AlGaN SCSLs is as the cladding layer of LDs . Because the refractive index is an important parameter that dominates light confinement, that of the SCSL was evaluated using spectroscopic ellipsometry.…”

“…Considering the large strain between the epilayers and GaN substrate, short period superlattices (SLs), where each component layer is thinner than its critical layer thickness, are of particular importance. Such stress‐compensated SLs (SCSLs) have been proposed for cladding layers of LDs , barriers in quantum well (QW) structures , and carrier‐blocking layers . However, a systematic study has yet to be performed on the design and fabrication of InGaN/AlGaN SCSLs, especially on semipolar planes.…”

III‐VCompound Semiconductor Optoelectronic Devices

“…Use of AlGaN/GaN multi quantum well barriers as carrier blocking layers has resulted in improved slope efficiency and reduced threshold currents in InGaN devices (65,66). The AlGaN/GaN barriers also reduce the effect of strain in the InGaN quantum well active region compared to quantum well structures capped with AlGaN (67). Use of Al containing superlattices in the GaN buffers (grown on sapphire substrates) has also resulted in improved device performance due to strain compensation and reduced threading dislocation density in the devices as Al containing layers act as filters for these dislocations (68).…”

Influence of AlGaN/GaN/InGaN superlattice on the characteristics of LEDs grown by metalorganic chemical vapor deposition

“…Recently, Czernecki et al suggested strain-compensated triple AlGaN/GaN/InGaN SLs to suppress the bowing and cracking in violet LDs [11]. These triple AlGaN/GaN/InGaN SLs were designed to compensate for the tensile stress of AlGaN caused by the compressive stress of InGaN with respect to GaN.…”