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Influence of width of left well in AlxGa1-xN/GaN double quantum wells (DQWs) on absorption coefficients and wavelengths of the intersubband transitions (ISBTs) is investigated by solving the Schrodinger and Poisson equations self-consistently. When the width of left well is 1.79nm, three-energy-level DQWs are realized. The ISBT between the first odd and second odd order subbands (the 1odd-2odd ISBT) has a comparable absorption coefficient with the 1odd-2even ISBT. Their wavelengths are located at 1.3 and 1.55μm, respectively. When the width of left well is 1.48nm, a four-energy-level DQWs is realized. The calculated results have a possible application to ultrafast two-colour optoelectronic devices operating within the optical communication wavelength range.

The influence of the polarization-induced electric field and other parameters on the subband structure in AlxGa1−xN /GaN coupled double quantum wells (DQWs) has been studied by solving the Schrodinger and Poisson equations self-consistently. It is found that the polarization effect leads to an asymmetric potential profile of AlxGa1−xN/GaN DQWs although the two wells have the same width and depth. The polarization effect also leads to a very large Stark shift between the odd and the even order subband levels that can reach 0.54 eV. Due to the polarization-induced Stark shift, the wavelength of the intersubband transition between the first odd order and the second even order subband levels becomes smaller, which is useful for realization of optoelectronic devices operating within the telecommunication window region.

Dependences of anticrossing gaps between pairs of subbands in AlxGa1−xN/GaN double quantum wells (DQWs) on the width and the Al composition of the central barrier of the DQWs and on the well width of the DQWs have been investigated by solving the Schrodinger and Poisson equations self-consistently. It is found that the anticrossing gaps are not influenced by the polarization-induced electric field in the DQWs. The anticrossing gaps decrease with increasing the width and the Al composition of the central barrier of the DQWs, as well as with the increasing well width of the DQWs. According to the results of the calculation, the anticrossing gaps can reach 150 meV in AlxGa1−xN/GaN DQWs. There is significant coupling between the two wells of the DQWs when the width of the central barrier of the DQWs is narrower than 2 nm.