Computation of the near-infrared electro-absorption in GeSn/SiGeSn step quantum wells

In this study, we propose a theoretical simulation of the type-I step quantum well obtained from GeSn/SiGeSn to scan a wide range of telecommunication wavelengths and obtain near-infrared optical modulators. At T = 300 K, the band discontinuities and energy gap between stretched Ge_1−xSn_x and relaxed Si_0.1Ge_0.9−ySn_y due to the acquisition of the heterostructure were calculated.

Then, optimization of this heterostructure based on (Si) GeSn was performed using the solid theory model to balance out the composition y of Si_0.1Ge_0.9-ySn_y relaxed and thickness of Ge_0.91Sn_0.09 QWs. The eigenenergies and their related wavefunctions are computed by solving the Schrödinger equation using the finite difference method under the framework of the effective mass approximation. Depending on the y concentration, the energy levels of the electron and the heavy hole, the change of transition energies and oscillator strength were examined for different well widths. Additionally, the absorption coefficient with y concentration and structure parameters were examined.

From the findings obtained, it was determined that this material group is very important to obtain high efficiency from electro-absorption modulators covering the 1.55 μm wavelength range.