Suppression of intersubband transition by applied electrical fields in AlN/GaN coupled double quantum wells

The influences of applied electrical fields on the absorption coefficient and subband energy distances of intersubband transitions (ISBTs) in AlN/GaN coupled double quantum wells (CDQWs) have been investigated by solving the Schrodinger and Poisson equations self-consistently. It is found that the absorption coefficient of the ISBT between the ground state and the second excited state (1_odd-2_odd) can be equal to zero when the electrical fields are applied in AlN/GaN CDQWs, which is related to applied electrical fields induced symmetry recovery of these states. Meanwhile, the energy distances between 1_odd-2_odd and 1_even-2_odd subbands have different relationships from each other with the increase of applied electrical fields due to the different polarization-induced potential drops between the left and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electrical fields in AlN/GaN CDQWs.