Electrically driven laser operation from InGaN based devices had been shown in wide optical range from UV to green. Applications of laser diodes (LDs) to data storage technology and laser projectors demand very high beam quality. Nitride based LDs suffer from leakage of optical modes to GaN substrate which is pronounced as ripples in the far field pattern [1] which significantly worsens the beam quality. The amount of light leaking to the substrate increases for LDs emitting at longer wavelengths.
Leakage of optical modes to GaN substrate is often reduced by increasing the n-type AlGaN cladding thickness. Strauss et al. had shown that for LDs emitting at λ=440 nm a cladding as thick as 3 µm is needed to fully suppress ripples in far field pattern and obtain a Gaussian shaped beam. Growth of such thick AlGaN claddings without cracks in the structure is demanding for epitaxy.
In this work we present another way to obtain Gaussian shaped far field pattern for blue LDs. We have grown AlGaN cladding free LDs by Plasma Assisted Molecular Beam Epitaxy (PAMBE) [3,4], where the optical mode is confined by thick, high In content InGaN waveguide. Growth of thick high quality InGaN layers needed for waveguides is crucial to obtain good LD characteristics. Recent advantages in understanding of growth mode of high In content InGaN layers by PAMBE [5] allowed us to obtain high quality InGaN waveguide.
Due to the fact that effective refractive index of the light propagating in InGaN waveguide is higher than refractive index of GaN there is no leakage of optical modes to the GaN substrate. We show Gaussian shaped far field patterns with no ripples. AlGaN cladding free blue and green LDs can prove to be the choice for new generation laser projectors.

[1] V. Laino et al., Substrate Modes of (Al,In)GaN Semiconductor Laser Diodes on SiC and GaN Substrates, IEEE Journal of Quantum Electronics, vol.43, no.1, pp.16,24, Jan. 2007 
[2] U. Strauss et al., Beam quality of blue InGaN laser for projection, Phys. Status Solidi C 5 (2008) 2077 
[3] C. Skierbiszewski et al., AlGaN-Free Laser Diodes by Plasma-Assisted Molecular Beam Epitaxy, Appl. Phys. Express 5 (2012) 022104
[4] C. Skierbiszewski et al., True-Blue Nitride Laser Diodes Grown by Plasma-Assisted Molecular Beam Epitaxy, Appl. Phys. Express 5 (2012) 112103
[5] H. Turski et al., Nonequivalent atomic step edges—Role of gallium and nitrogen atoms in the growth of InGaN layers, Journal of Crystal Growth, Volume 367, 15 March 2013, Pages 115-121

Acknowledgements: This work was supported partially by the Polish Ministry of Science and Higher Education Grants No IT 13426 and INNOTECH 157829.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/29792 must be provided.

1. Semipolar and nonpolar AlGaN growth mechanisms under N-rich conditions in PAMBE
2. Indium incorporation mechanism during InGaN growth by plasma-assisted molecular beam epitaxy
3. Semipolar (2021) UV LEDs and LDs grown by PAMBE
4. X-ray measurements of type II InAs/GaSb superlattice in a wide angular range using the P08 beamline at PETRAIII
5. Efficiency „droop” in nitride light emitters
6. Functionalized cobalt nanoparticles
7. Surface morphology of InGaN layers
8. TEM investigation of processed  InGaN based laser grown by PAMBE on bulk GaN substrate
9. High pulse power mid-infrared AlGaAs/GaAs quantum cascade lasers
10. Blue laser diodes by low temperature plasma assisted MBE
11. Low temperature plasma assisted MBE growth for nitride optoelectronic devices
12. Microstructure of homoepitaxially grown InGaN/GaN, violet light emitting laser diodes.
13. Anomalous behaviour of the photoluminescence from GaN/AlGaN quantum wells
14. Built-in electric fields in group III-nitride light emitting quantum structures
15. MBE growth and characterization of InAs/GaAs for infrared detectors
16. The optimalisation of the GaN and GaN/AlGaN heterojunctions on bulk crystals using plasma-assisted molecular beam epitaxy
17. Homoepitaxy of GaN-based blue and UV lasers
18. Sensitive InGaAs /InP (SI) magnetic field sensors
19. PT-Phase Diagram of Sn2P2S6 Crystals, Photoluminescence and Fundamental Absorbtion Edge