First-Principle Electronic Properties of Dilute-P GaN1−xPx Alloy for Visible Light Emitters

Abstract

A study on the electronic properties of the dilute-P GaN1−xPx alloy using First-Principle Density Functional Theory (DFT) calculations is presented. Our results indicate a band gap energy coverage from 3.645 eV to 2.697 eV, with P-content varying from 0% to 12.5% respectively. In addition, through line fitting of calculated and experimental data, a bowing parameter of 9.5 ± 0.5 eV was obtained. The effective masses for electrons and holes are analyzed, as well as the split-off energy parameters where findings indicate minimal interband Auger recombination. The alloy also possesses the direct energy band gap property, indicating its strong potential as a candidate for future photonic device applications.

First-Principle Study of the Optical Properties of Dilute-P GaN1−xPx Alloys

“…Similar to the xy-direction, the increase of the refractive index in the z-direction as compared to DFT-calculated GaN can be significant (~0.3). Moreover, for both, the xy- and z-directions, increasing the phosphorus content in the dilute-P GaNP alloys shifts the band edge peaks towards the lower photon energies which is in agreement with the energy gap reduction reported previously, where the 12.5% P-containing GaNP alloy has a band edge peak around ~ 2.7 eV 32 . In other conventional III-nitride material systems like AlGaN, the refractive index is also a linear function of the Al-content, as is for the case of the dilute-As GaNAs alloys 57,71 .…”

“…Moreover, increasing the phosphorus content shifts the spectra towards lower photon energies, which is similar to the case of the xy-direction. Figure 2(b) indicates that the onset of the imaginary part of the dielectric function for the 12.5% P-containing alloy is around ~2.7 eV, which is in good agreement with the energy band gap reported by Tan and co-workers 32 . Additionally, note that the E1–E3 group of absorption peaks has been reported to correspond mostly to optical transitions near M , but contributions from U , S ’, Σ, H and K points in the BZ are present 63 .…”

“…The phenomenon shown in Fig. 2(a) is directly related to the decrease in energy band gap when P-content increases in dilute-P GaNP alloys, which has been observed experimentally and theoretically 32,36 . Figure 2(a) also shows the E1, E2 and E3 absorption peaks for GaN occurring at around 7.8 eV, 8.3 eV and 9.1 eV, respectively, aligning well with previously reported values in which E1, E2 and E3 peaks are positioned around 7.5 eV, 7.9 eV and 9 eV, respectively 61,62 .…”

“…The Fig. 5(a,b) indicate that the increase in the phosphorus content perturbs the k xy and k z spectra significantly and shifts the onsets of absorption to lower photon energies, which is also related to the changes in the band structure of the dilute-P GaNP material system 32 . It has been shown previously that the P-impurity level lies above the top-most valence band of GaN (~0.2 eV), and that the introduction of P atoms leads to an upward movement of the top-most valence band due to the formation of localized P states 43,73 .…”

“…Secondly, the quest to push for longer wavelength emission beyond the green spectral regime by using In x Ga 1−x N-based devices has been stagnating, mainly attributed to material quality issues at high indium contents (x > 0.2), resulting in low external quantum efficiencies (EQE) ~ 4% of the red-emitting LEDs 21–25 . Several methods have been proposed to overcome the two issues, which includes innovative material systems and active region design suitable for emission in the longer wavelength regimes 26–32 . Recently, dilute-anion III-nitride semiconductors such as dilute-As GaNAs and dilute-P GaNP have been suggested as alternative candidates to InGaN, due to their highly desirable electronic properties, including the possibility to suppress the Auger recombination rate and capability to push for longer wavelength emission 31–33 .…”