Optical properties of an InGaAs-InP interdiffused quantum well

A comprehensive model is developed for the calculation of polarization-dependent absorption coefficients and refractive index of the InGaAs-InP interdiffused multiple-quantum-well at room temperature for wavelengths ranging from 1.1 to 2.4 μm. Groups III and V types of interdiffusion are considered separately. The as-grown structure is a latticed-matched In_0.53Ga_0.47As-InP structure with a well width of 60 Å. The optical transitions consist of a full quantum-well calculation together with Γ,X, and L valleys contributions and through the Kramers-Kronig transformation to link the real and imaginary parts of the dielectric functions. The results show that group-III-only interdiffusion produces compressive strain and results in a band-edge red shift and refractive index enlargement, while the tensile strain induced by group-V-only interdiffusion results in a vice verse effect. This provides a left and right tunable band edge and positive and negative index steps dependent on the interdiffusion process. A small and constant birefringence of 0.005 at around 1.55 μm can also be obtained over a 50-nm wavelength range by using group-V-only interdiffusion. These properties have strong implications in realizing a tunable and high-performance device as well as for photonic integrations