New take-off of Gallium Nitride

Abstract

Gallium Nitride (GaN) is a wide-band-gap semiconductor compound (Eg = 3.4 eV at 300 K) which over the last decades played a major role in the development of modern solid-state lighting industry. An intensive investigation of this compound started in the 70-ies of the last century, but without visible success in pushing real applications. In the absence of native bulk material, GaN epilayers were grown on foreign substrates and, as a result of the large lattice mismatch and difference in thermal expansion coefficients, the overgrown films contained a high amount of threading dislocations. The fascinating point, however, is that even in the presence of huge amounts of dislocations, sometimes exceeding 1010 cm-2, gallium nitride exhibits intense luminescence, a property that makes the compound unique in comparison with other III-V materials as, for instance, GaAs, GaP and InP. GaN-based blue light emitting diodes have been developed by middle of 90-ies and subsequently commercialized successfully. No doubt that lighting technologies based on GaN and related nitrides will continue their impactful evolution, especially taking into account the recent demonstration of electrically pumped inversionless polariton lasing at room temperature from a bulk GaN-based microcavity diode (P. Battacharya et al, Phys. Rev. Lett. 112, 236802, 2014). Novel developments based on GaN nanostructures will be presented in the report.