Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

J. T. Leonard, B. P. Yonkee, D. A. Cohen, L. Megalini, S. Lee, J. S. Speck, S. P. DenBaars, S. Nakamura

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34 Scopus citations

Abstract

We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm2 (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP12,1), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.
Original languageEnglish (US)
Pages (from-to)031111
JournalApplied Physics Letters
Volume108
Issue number3
DOIs
StatePublished - Jan 18 2016
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors would like to thank Mitsubishi Chemical Corporation for providing high-quality free-standing m-plane GaN substrates. This work was funded in part by the King Abdulaziz City for Science and Technology (KACST) Technology Innovations Center (TIC) program and the Solid State Lighting and Energy Electronics Center (SSLEEC) at the University of California, Santa Barbara (UCSB). Partial funding for this work came from Professor Boon S. Ooi at King Abdullah University of Science and Technology (KAUST), through his participation in the KACST-TIC program. A portion of this work was done in the UCSB nanofabrication facility, with the support from the NSF NNIN network (ECS-03357650), the UCSB Materials Research Laboratory (MRL), which was supported by the NSF MRSEC program (DMR-1121053), and the California NanoSystem Institute's (CNSIs) Center for Scientific Computing at UCSB.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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