Influence of structure and doping concentration of AlxGa1-xN/GaN double quantum wells on wavelength and absorption coefficient of intersubband transitions

Abstract

By solving the Schrdinger and Poisson equations self-consistently, the central barrier height, central barrier width, well width, and doping concentration in the barriers of symmetric Al0.75Ga0.25N/GaN double quantum wells (DQWs) have been studied to investigate their influences on the wavelength and absorption coefficient of intersubband transitions (ISBTs). A smaller wavelength of the ISBT between the first odd and the second even order subbands (S1odd-S2even ISBT) in Al0.75Ga0.25N/GaN DQWs and a larger absorption coefficient of the S1odd-S2even ISBT were obtained with decreased central barrier height, when the central barrier height was larger than 0.62 eV. The wavelength of the S1odd-S2even ISBT decreases, and the absorption coefficient of the S1odd-S2even ISBT increases, when the width of the central barrier is reduced. On the other hand, decreasing the width of the well will result in smaller wavelength of the S1odd-S2even ISBT and larger absorption coefficient of the S1odd-S2even ISBT when the width of the well is narrower than 1.9 nm. When doping concentration in the barriers is smaller than 1018/cm3， the wavelength of the S1odd-S2even ISBT is unchanged, while the absorption coefficient of the S1odd-S2even ISBT increases with the doping concentration. These results provide useful guidance for realization of ultrafast two-color optoelectronic devices operating in the optical communication wavelength range.