MOVPE Growth and Doping Optimization of n-AlGaAs Layers for Laser Diode Applications

Epitaxial n-AlₓGa₁₋ₓAs layers, which form the basis of semiconductor laser structures, play a critical role in both optical and electrical performance of the device. These layers provide electron injection into the active region and at the same time act as optical waveguides, allowing efficient steering of the laser light. Since Al concentration and doping levels have a direct effect on fundamental properties such as band gap, carrier density and resistive losses, it is of great importance to meticulously optimize these parameters. In this study, n-AlₓGa₁₋ₓAs layers grown epitaxially on GaAs substrate by MOVPE (Metal Organic Vapor Phase Epitaxy) method were processed with n-type doping process applied by using SiH₄ precursor and the effects of increasing Al concentration on doping density were investigated in detail. The obtained results show that when Al concentration is above 30%, no significant increase in doping density is observed despite the maximization of SiH₄ flow. Furthermore, the data obtained with Hall and ECV (Electrochemical Capacitance Voltage) measurements provided consistent results at low Al ratios, while significant differences were observed above 0.2 Al ratio. This comprehensive analysis reveals the current limitations in n-type doping processes and precise control of Al concentration, while providing a more in-depth interpretation by systematically comparing the obtained results with the data reported in the literature.