GaN/AlN multiple quantum wells and waveguide fabrication for ultrafast photonic devices utilizing intersubband transition

Intersubband transition in GaN/AIN multiple quantum well (MQW) structures was demonstrated with metal-organic vapour phase epitaxy (MOVPE) in a wavelength range of 2.4-3.5 μm by varying the quantum well with constant barrier width. The linewidths of intersubband absorption are approximately 70 meV, indicating excellent quality of the MOVPE-grown samples. In addition to performing epitaxial growth, we calculated the intersubband absorption taking into account built-in electric field in the MQW structures. Based on optical characterization results, the induced built-in electric field in the MQW structures was found to be very strong in the order of 2-3 MV/cm. Moreover, we demonstrated the fabrication of ridge waveguide and high-mesa waveguide on the MQW samples, and successfully performed optical waveguide measurement, showing possibility to make high performance intersubband transition devices.