• F. Reveret, K. Bejtka, P. R. Edwards, S. Chenot, I. R. Sellers, P. Disseix, A. Vasson, J. Leymarie, J. Y. Duboz, M. Leroux, F. Semond, and R. Martin, “Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods,” Journal of Applied Physics, vol. 108, iss. 4, p. 43524, 2010.

Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on (111) Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al0.2Ga0.8N / AlN Bragg mirror followed by a lambda/2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2,mu m thick GaN layer is grown, and progressively thinned to a final thickness of lambda. Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3477450]

@Article{strathprints28963,
author = {F. Reveret and K. Bejtka and P. R. Edwards and S. Chenot and I. R. Sellers and P. Disseix and A. Vasson and J. Leymarie and J. Y. Duboz and M. Leroux and F. Semond and Robert Martin},
title = {Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods},
journal = {Journal of Applied Physics},
year = {2010},
volume = {108},
number = {4},
pages = {043524},
month = {August},
abstract = {Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on (111) Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al0.2Ga0.8N / AlN Bragg mirror followed by a lambda/2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2,mu m thick GaN layer is grown, and progressively thinned to a final thickness of lambda. Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3477450]},
keywords = {semiconductor microcavities, laser, aluminium compounds, distributed Bragg reflectors, gallium compounds, molecular beam epitaxial growth, photoluminescence, semiconductor growth , wide band gap semiconductors, Physics, Physics and Astronomy(all)},
url = {http://strathprints.strath.ac.uk/28963/}
}

• K. Bejtka, F. Reveret, R. W. Martin, P. Edwards, A. Vasson, J. Leymarie, I. R. Sellers, and J. Y. Duboz, “Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities,” Applied Physics Letters, vol. 92, iss. 24, p. 241105, 2008.

Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The {\ensuremath{\lambda}}/2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5 K: anticrossing with a normal mode splitting of 43{$\pm$}2 meV and 56{$\pm$}2 meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance.

@Article{strathprints19621,
author = {K. Bejtka and F. Reveret and R.W. Martin and Paul Edwards and A. Vasson and J. Leymarie and I.R. Sellers and J.Y. Duboz},
title = {Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities},
journal = {Applied Physics Letters},
year = {2008},
volume = {92},
number = {24},
pages = {241105},
month = {June},
note = {Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.},
abstract = {Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The {\ensuremath{\lambda}}/2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5 K: anticrossing with a normal mode splitting of 43{$\pm$}2 meV and 56{$\pm$}2 meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance.},
keywords = {semiconductor microcavities, photoluminescence, light-matter coupling, double dielectric mirror, GaN, Optics. Light, Physics and Astronomy (miscellaneous)},
url = {http://strathprints.strath.ac.uk/19621/}
}

• F. Rizzi, P. R. Edwards, K. Bejtka, F. Semond, E. Gu, M. D. Dawson, I. M. Watson, and R. W. Martin, “Double dielectric mirror InGaN/GaN microactivities formed using selective removal of an AlInN layer,” Superlattices and Microstructures, vol. 41, iss. 5-6, p. 414, 2007.

We describe the fabrication and optical properties of a 3{\ensuremath{\lambda}}/2 InGaN/GaN-based microcavity using “upper” and “lower” silica/zirconia mirrors. The fabrication of this structure involved selective removal of an AlInN layer following multistep thinning of a free-standing GaN substrate. Photoluminescence spectra show a narrowing of the excitonic emission from InGaN/GaN quantum wells in the microcavity, giving a cavity quality factor Q exceeding 400.

@article{strathprints8974,
volume = {41},
number = {5-6},
month = {June},
author = {F. Rizzi and P.R. Edwards and K. Bejtka and F. Semond and E. Gu and M.D. Dawson and I.M. Watson and R.W. Martin},
title = {Double dielectric mirror InGaN/GaN microactivities formed using selective removal of an AlInN layer},
journal = {Superlattices and Microstructures},
pages = {414},
year = {2007},
keywords = {GaN, InGaN, AlInN, quantum well, microcavity, wet etching, reflectance, cathodoluminescence, photoluminescence, Optics. Light, Materials Science(all), Electrical and Electronic Engineering, Condensed Matter Physics},
url = {http://strathprints.strath.ac.uk/8974/},
abstract = {We describe the fabrication and optical properties of a 3{\ensuremath{\lambda}}/2 InGaN/GaN-based microcavity using "upper" and "lower" silica/zirconia mirrors. The fabrication of this structure involved selective removal of an AlInN layer following multistep thinning of a free-standing GaN substrate. Photoluminescence spectra show a narrowing of the excitonic emission from InGaN/GaN quantum wells in the microcavity, giving a cavity quality factor Q exceeding 400.}
}

• F. Rizzi, P. R. Edwards, K. Bejtka, F. Semond, X. N. Kang, G. Y. Zhang, E. Gu, M. D. Dawson, I. M. Watson, and R. W. Martin, “(In,Ga)N/GaN microcavities with double dielectric mirrors fabricated by selective removal of an (Al,In)N sacrificial layer,” Applied Physics Letters, vol. 90, iss. 11, p. 111112, 2007.

Comparable microcavities with 3/2 ({\texttt{\char126}}240 nm) active regions containing distributed (In,Ga)N quantum wells, grown on GaN substrates and bounded by two dielectric mirrors, have been fabricated by two different routes: one using laser lift-off to process structures grown on GaN-on-sapphire templates and the second using freestanding GaN substrates, which are initially processed by mechanical thinning. Both exploit the properties of an Al0.83In0.17N layer, lattice matched to the GaN substrate and spacer layers. In both cases cavity quality factors {\ensuremath{>}}400 are demonstrated by measurements of the cavity-filtered room-temperature excitonic emission near 410 nm.

@Article{strathprints9055,
author = {F. Rizzi and P.R. Edwards and K. Bejtka and F. Semond and X.N. Kang and G.Y. Zhang and E. Gu and M.D. Dawson and I.M. Watson and R.W. Martin},
title = {(In,Ga)N/GaN microcavities with double dielectric mirrors fabricated by selective removal of an (Al,In)N sacrificial layer},
journal = {Applied Physics Letters},
year = {2007},
volume = {90},
number = {11},
pages = {111112},
month = {March},
abstract = {Comparable microcavities with 3/2 ({\texttt{\char126}}240 nm) active regions containing distributed (In,Ga)N quantum wells, grown on GaN substrates and bounded by two dielectric mirrors, have been fabricated by two different routes: one using laser lift-off to process structures grown on GaN-on-sapphire templates and the second using freestanding GaN substrates, which are initially processed by mechanical thinning. Both exploit the properties of an Al0.83In0.17N layer, lattice matched to the GaN substrate and spacer layers. In both cases cavity quality factors {\ensuremath{>}}400 are demonstrated by measurements of the cavity-filtered room-temperature excitonic emission near 410 nm.},
keywords = {gallium compounds, indium compounds, wide band gap semiconductors, quantum well lasers, microcavity lasers, micromirrors, laser mirrors, optical fabrication, laser materials processing, Optics. Light, Physics and Astronomy (miscellaneous)},
url = {http://strathprints.strath.ac.uk/9055/}
}

• F. Rizzi, K. Bejtka, F. Semond, E. Gu, M. D. Dawson, I. M. Watson, and R. W. Martin, “Dry etching of n-face GaN using two high-density plasma etch techniques,” Physica Status Solidi C, vol. 4, iss. 1, p. 200–2003, 2007.

This paper describes processing of GaN on the on the (000I) N-face surface, using two different high-density plasma etch techniques, inductively coupled plasma (ICP) etch, and electron cyclotron resonance (ECR) etching. ICP experiments used several different conditions employing Cl2-Ar-BCl3 or Cl2-Ar plasmas. The resulting maximum etch rates of 370-390 nm/min are approximately twice as high as etch rates for Ga-face (0001) GaN with the same recipes. ECR etching employed a Cl2-CH4-Ar recipe, which produced an average etch rate of 55 nm/min in a 20-minute etch process on N-face GaN. Both etch techniques increased the roughness of N-face GaN, but could produce surfaces with average roughness values below 3 nm. Selection of conditions with a dominant chemical etch contribution is important to maintain smooth surfaces. The use of both ICP and ECR etching in sequence is advantageous in situations where a GaN substrate several tens of microns in thickness must be thinned from the backside, stopping the etch in a suitable marker layer.

@article{strathprints9111,
volume = {4},
number = {1},
title = {Dry etching of n-face GaN using two high-density plasma etch techniques},
author = {F. Rizzi and K. Bejtka and F. Semond and E. Gu and M.D. Dawson and I.M. Watson and R.W. Martin},
year = {2007},
pages = {200--2003},
journal = {Physica Status Solidi C},
keywords = {high-density plasma, dry etching, etch techniques, inductively coupled plasma, electron cyclotron resonance, Optics. Light, Condensed Matter Physics},
url = {http://strathprints.strath.ac.uk/9111/},
abstract = {This paper describes processing of GaN on the on the (000I) N-face surface, using two different high-density plasma etch techniques, inductively coupled plasma (ICP) etch, and electron cyclotron resonance (ECR) etching. ICP experiments used several different conditions employing Cl2-Ar-BCl3 or Cl2-Ar plasmas. The resulting maximum etch rates of 370-390 nm/min are approximately twice as high as etch rates for Ga-face (0001) GaN with the same recipes. ECR etching employed a Cl2-CH4-Ar recipe, which produced an average etch rate of 55 nm/min in a 20-minute etch process on N-face GaN. Both etch techniques increased the roughness of N-face GaN, but could produce surfaces with average roughness values below 3 nm. Selection of conditions with a dominant chemical etch contribution is important to maintain smooth surfaces. The use of both ICP and ECR etching in sequence is advantageous in situations where a GaN substrate several tens of microns in thickness must be thinned from the backside, stopping the etch in a suitable marker layer.}
}

• K. Bejtka, F. Rizzi, P. R. Edwards, R. W. Martin, E. Gu, M. D. Dawson, I. M. Watson, I. R. Sellers, and F. Semond, “Roles for aluminium indium nitride insertion layers in fabrication of GaN-based microcavities,” Physica Status Solidi A: Applications and Materials Science, vol. 202, iss. 14, p. 2648–2652, 2005.

AlInN alloys achieve an in-plane lattice match to hexagonal GaN at an indium nitride mole fraction of 18\%. Meanwhile Al0.82In0.18N displays a refractive index contrast of 7\% with GaN at visible wavelengths. We illustrate the use of Al0.82In0.18N insertion layers to control layer thicknesses during homoepitaxial growth of GaN-based microcavities, using in situ optical reflectometry. The structures discussed are 3 /2 microcavities incorporating distributed InGaN quantum wells tailored for emission at 400 nm. As-grown samples have been characterised by techniques including cathodoluminescence spectroscopy. In addition to their role in growth monitoring, there are several post-growth processing steps in which Al0.82In0.18N insertion layers can assist microcavity fabrication. We focus here on a demonstration of the 1:5 etch rate selectivity obtainable between Al0.82In0.18{\ensuremath{<}}/SUB {\ensuremath{>}}N and GaN in reactive ion etching

@article{strathprints10016,
volume = {202},
number = {14},
month = {November},
author = {K. Bejtka and F. Rizzi and P.R. Edwards and R.W. Martin and E. Gu and M.D. Dawson and I.M. Watson and I.R. Sellers and F. Semond},
title = {Roles for aluminium indium nitride insertion layers in fabrication of GaN-based microcavities},
journal = {Physica Status Solidi A: Applications and Materials Science},
pages = {2648--2652},
year = {2005},
keywords = {78.60.Hk, , plasma, lasers, 81.65.Cn , 81.15.Gh, , 81.05.Ea, , 78.67.De, , Physics, Electronic, Optical and Magnetic Materials, Condensed Matter Physics},
url = {http://strathprints.strath.ac.uk/10016/},
abstract = {AlInN alloys achieve an in-plane lattice match to hexagonal GaN at an indium nitride mole fraction of 18\%. Meanwhile Al0.82In0.18N displays a refractive index contrast of 7\% with GaN at visible wavelengths. We illustrate the use of Al0.82In0.18N insertion layers to control layer thicknesses during homoepitaxial growth of GaN-based microcavities, using in situ optical reflectometry. The structures discussed are 3 /2 microcavities incorporating distributed InGaN quantum wells tailored for emission at 400 nm. As-grown samples have been characterised by techniques including cathodoluminescence spectroscopy. In addition to their role in growth monitoring, there are several post-growth processing steps in which Al0.82In0.18N insertion layers can assist microcavity fabrication. We focus here on a demonstration of the 1:5 etch rate selectivity obtainable between Al0.82In0.18{\ensuremath{<}}/SUB {\ensuremath{>}}N and GaN in reactive ion etching}
}