Void engineering in epitaxially regrown GaAs-based photonic crystal surface emitting lasers by grating profile design

Abstract

We report the engineering of air voids embedded in GaAs-based photonic crystal surface-emitting lasers realized by metalorganic vapor-phase epitaxy regrowth. Two distinct void geometries are obtained by modifying the photonic crystal grating profile within the reactor prior to regrowth. The mechanism of void formation is inferred from scanning transmission electron microscopy analysis, with the evolution of the growth front illustrated though the use of an AlAs/GaAs superlattice structure. Competition between rapid lateral growth of the (100) surface and slow diffusion across higher index planes is exploited in order to increase the void volume, leading to an order of magnitude reduction in threshold current and an increase in output power through an increase in the associated grating coupling strength.

Study of an Epitaxial Regrowth Process by MOCVD for Photonic-Crystal Surface-Emitting Lasers

“…For samples A and C, even the etching depth varied a lot, the upper parts of the air-hole shape were very similar, and the height of the dome top of air voids was nearly identical. The geometries indicated that the coalesce of the air voids is determined by the lateral growth through the (100) plane on the plateau of the PC region, the growth through the {100} plane of the side wall, and through the higher index plane indicated by the yellow dashed line . The initial high growth rate was intended to enhance the growth along the [001] direction over the lateral growth to retain the air voids.…”

“…The geometries indicated that the coalesce of the air voids is determined by the lateral growth through the (100) plane on the plateau of the PC region, the growth through the {100} plane of the side wall, and through the higher index plane indicated by the yellow dashed line. 25 The initial high growth rate was intended to enhance the growth along the [001] direction over the lateral growth to retain the air voids. Sample B was grown using a thicker faster growth stage than the other two samples; however, the variation of the geometry of the air voids is not obvious.…”

Small signal modulation of photonic crystal surface emitting lasers

“…Historically PCSELs have been formed by wafer fusion, but these devices suffered from low output powers due to defect states in the PC region as a result of regions of discontinuous crystallinity formed during the wafer fusion process 7 – 9 . More recently our group 10 – 12 along with several others have demonstrated PCSELs formed by epitaxial regrowth 13 – 17 . The move to epitaxial regrowth by metalorganic vapour phase epitaxy (MOVPE) has demonstrated a pathway to high volume production of highly reliable devices leveraging all the knowledge gained over many years of InP DFB development.…”

Continuous wave room temperature operation of the GaSb-based photonic crystal surface emitting diode lasers

“…Thin layer of AlGaAsSb material covers etched GaSb surface even inside of the etched holes. However, the self-shadowing of the etched holes from atomic fluxes incoming at the angle to surface normal and tendency of (100) surfaces to promote lateral growth due to higher adatom surface mobility (compared to high index surfaces) [8] leads to merging of the growth fronts and formation of the buried voids. As a result, air-pockets were encapsulated within ~500 nm of the p-cladding material.…”