Abstract
An investigation on the optical properties of dilute-P GaN1−xPx alloys by First-Principle Density Functional Theory (DFT) methods is presented, for phosphorus (P) content varying from 0% up to 12.5%. Findings on the imaginary and real part of the dielectric function are analyzed and the results are compared with previously reported theoretical works on GaN. The complex refractive index, normal-incidence reflectivity and birefringence are presented and a difference in the refractive index in the visible regime between GaN and GaNP alloys of ~0.3 can be engineered by adding minute amounts of phosphorus, indicating strong potential for refractive index tunability. The optical properties of the GaN1−xPx alloys indicate their strong potential for implementation in various III-nitride-based photonic waveguide applications and Distributed Bragg Reflectors (DBR).
Highlights
The soaring interest for the advancement of III-nitride semiconductors has been primarily driven by their highly desirable electronic, optoelectronic, chemical and tribological properties, suitable for a wide range of applications[1,2,3,4,5,6,7,8]
By using the Kramers-Kronig relation, the real and imaginary parts of the complex dielectric function are described as follows[58]: Figure 2. (a) Imaginary part of the dielectric function for E ⊥ c direction (ε2,xy(E)) and (b) E ‖ c direction (ε2,Z(E)) spectra for dilute-P GaNP alloys, with P-content varying from 0% up to 12.5% phosphorus, respectively
Optical properties calculations of dilute-P GaNP semiconductor alloys with P-content varying from 0% to 12.5% have been performed by employing First-Principle Density Functional Theory (DFT) calculations with the Local Density Approximation (LDA) approximation
Summary
The soaring interest for the advancement of III-nitride semiconductors has been primarily driven by their highly desirable electronic, optoelectronic, chemical and tribological properties, suitable for a wide range of applications[1,2,3,4,5,6,7,8]. The quest to push for longer wavelength emission beyond the green spectral regime by using InxGa1−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 LEDs21–25. 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[31,32,33]. The promising electronic properties of the dilute-P GaNP semiconductor and its experimental feasibility pose it as an excellent candidate for applications for visible light emission. It is of great importance to understand the underlying optical properties of the dilute-P GaNP alloys and their implication for future design of III-nitride-based photonic devices
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