Light-emitting diodes based on wurtzite (wz) InGaN/GaN quantum wells (QWs) have achieved great success in the blue spectral region, with reported external quantum efficiencies exceeding 80 %¹.  However, the efficiency of the QWs significantly decreases when attempting to extend the emission to the longer wavelengths needed to realise the next generation of RGB display technology².  The increased indium content – needed to tune the emission to longer wavelengths - exacerbates the quantum confined Stark effect present in the material, and the lower growth temperature needed to incorporate indium leads to a higher density of luminescence killing point defects in the material³.  An attractive alternative for longer wavelength emitters is InGaN/GaN QWs in the zincblende (zb) phase - which lack polarisation fields⁴, have an intrinsically lower bandgap than their wz counterpart, and have been shown to emit across the visible spectrum by varying the indium content within the QW layers⁵.  However, there is currently a lack of understanding of the effect of indium content on the emission efficiency of zb-QWs.   Thus, to fully understand the potential of this material to realise the next generation of RGB display technology, these effects will have to be elucidated by monitoring the emission response to sample temperature and excitation density.  

The samples in this study consisted of five quantum wells, each 2.5 nm thick, grown by metal organic chemical vapor deposition, with the growth temperature of the quantum well layer altered to increase the indium content, and thus tune the emission across the visible spectrum (see photoluminescence spectra shown in Figure 1). 

References

¹Y. Narukawa et al., J. Phys. D. 43, 354002 (2010)

²B. Ding, Materials Science and Technology, 34:14, 1615 (2018)

³S. Hammersley et al. Phys. Status Solidi C. 13, 209 (2016)

⁴D. R. Elsaesser et al., J. Appl. Phys. 122, 115703 (2017)

⁵I. E. Orozco Hinostroza et al. J. Cryst. Growth. 435, 110 (2016)