Designs of blue and green light-emitting diodes based on type-II InGaN-ZnGeN2 quantum wells

Type-II InGaN-ZnGeN2 quantum wells (QWs) are studied as improved active regions for light-emitting diodes emitting in the blue (λ ∼ 485 nm) and green (λ ∼ 530 nm) spectral ranges. Both the energy band gap and the lattice parameters of ZnGeN2 are very close to those of GaN. The recently predicted large band offset between GaN and ZnGeN2 allows the formation of a type-II InGaN-ZnGeN2 heterostructure. The strong confinement of holes in the ZnGeN2 layer allows the use of a lower In-content InGaN QW to extend the emission wavelength into the blue and green wavelength regions, as compared to the traditional InGaN QW with uniform In content. In the type-II InGaN-ZnGeN2 QW designs, a thin AlGaN layer was used as a barrier for better carrier confinement. The type-II InGaN-ZnGeN2 QWs lead to a significant enhancement of the electron-hole wave function overlap as compared to those of the conventional QWs. Simulation studies of the proposed type-II QWs promise a significant enhancement of the spontaneous emission rate by 6.1–7.2 times for the QW design emitting at the blue wavelength region and 4.6–4.9 times for the QW design emitting at the green wavelength region, as compared to the conventional InGaN QWs emitting at the same wavelengths.