Intersubband transitions in asymmetric AlxGa1-xN/GaN double quantum wells.

Influence of the width and Al composition of one well in asymmetric Al0.85Ga0.15N/GaN double quantum wells (DQWs) on the absorption coefficients and the wavelengths of the intersubband transitions (ISBTs) has been investigated by solving the Schrödinger and Poisson equations self-consistently. When the well width is chosen to be 1.91 nm, the three-energy-level DQWs are realized. The ISBT between the first odd order and the second even order subbands (the 1odd-2even ISBT) has comparable absorption coefficient with the 1odd-2odd ISBT. Their wavelengths are located at 1.3 and 1.54 μm, respectively. When the well width is 2.77 nm, the four-energy-level DQWs are realized. The 1odd-2even and the 1even-2odd ISBTs have comparable absorption coefficients. Their wavelengths are located at 1.41 and 2.54 μm, respectively. The energy separation between the excited subbands is determined to have the minimum value of 144 meV due to the band anticrossing interaction. The calculated results give possible application to ultrafast two-color optoelectronic devices operating within the optical communication wavelength range. [ABSTRACT FROM AUTHOR]