Optical Gain Optimization of Al0.8Ga0.2N-Delta-GaN Quantum Well Laser in Ultraviolet Spectra Using Genetic Algorithm

In this work, AlGaN based quantum well laser has been designed with delta layer and characterized the designed laser structure. After the characterization, Genetic Algorithm process has been performed over optical gain to optimize it. In this design, AlN has been used as barrier material, Al_0.8Ga_0.2N has been utilized as active region material and GaN layer has been used as delta layer. For optimization, well width, delta layer width and barrier width have been taken as the variable for which genetic algorithm has performed the optimization process. Characterization of the designed laser shows good agreement with previously published works. Optimization of optical gain for both TE and TM gain also exhibits good improved result than previously published works. From characterization, it is found that the designed laser structure gives peak optical gain of 3589.5 cm⁻¹ and peak spontaneous emission rate of 12.94×10²⁸ s^-1cm^-3eV^-1 at 246.89 nm for 5×10¹⁹ cm^-3 carrier density. From optimization, it is obtained that optimum TE optical gain is found 6479.1 cm^-1 for 11 Å of QW along with 7 Å delta layer at 279 nm wavelength and optimum TM gain is found found 116.95 cm^-1 for 20 Å of QW along with 3 Å delta layer at 289.8 nm wavelength. In this work, electronic characterization has been performed with 6 band k.p Hamiltonian for valence subband calculation including valence band mixing effect, strain effect due to lattice mismatch, spontaneous and piezoelectric polarization. For conduction subband calculation, single band Hamiltonian has been solved with strain and polarization effect.