Cubic zincblende phase InGaN/GaN LEDs show promise as an alternative to hexagonal wurtzite phase
devices. These LEDs, with lower indium requirements for green emission [1], can be combined with
blue wurtzite InGaN/GaN and red InGaAlP LEDs for white lighting [2]. The recombination lifetime in
cubic quantum wells (QWs) is shorter than in wurtzite, reducing carrier density (alleviating efficiency
droop) and allowing rapid modulation for LiFi communications [3].
The sample, grown on a [001] 3C-SiC/Si substrate, features five 2.5 nm InGaN QWs on an 800 nm
zincblende GaN buffer layer [4]. Temperature-dependent photoluminescence (PL) spectroscopy was
conducted with a He-Cd laser at 325 nm and time correlated single photon counting PL was conducted
at 266nm between 12 and 300 K. The peak energy, integrated intensity over power density, and full
width half maximum (FWHM) were found for the PL spectra. The sample studied shows a shift from
excitation power dependent behaviour at low temperature to power independent behaviour at higher
temperatures.
At 12 K, the peak energy is 29 meV higher for high power than low power, however, peak energy is
the same for all powers above 150 K. At 12 K, emission efficiency droop is evident for higher excitation
powers, however, this dependence is negligible above 150 K indicating that the sample is not in the
droop regime. Efficiency drops to ≲ 2% of low temperature at 300 K for all powers. The FWHM
decreases with increasing temperature up to 200 K for low powers and stays stable for the highest
power. Above 200 K the FWHM increases due to increased thermal energy. The 1/e time decays are
relatively stable under 150 K, however, the lifetime begins to decrease after this point dropping to 30%
of its 12 K value at 300 K.
References.
[1] D. J. Binks, P. Dawson, R. A. Oliver, and D. J. Wallis. Appl. Phys. Rev., 9(4), 041309 (2022)
[2] J. Li and G. Q. Zhang. Solid State Lighting Technology and Application Series Light-Emitting Diodes
Materials, Processes, Devices and Applications (Springer, 2019).
[3] H. Haas, L. Yin, Y. Wang, and C. Chen, “What is LiFi?” J. Light. Technol., 34, 6, 1533–1544, (2016)
[4] S. A. Church et al. J. Appl. Phys., 129, 175702 (2021)