Ultrashort (/spl les/150 fs) carrier relaxation time of intersubband transition in AlGaN/GaN multiple quantum wells

Summary form only given. Intersubband transition (ISBT) in semiconductor multiple quantum wells (MQWs) is a promising phenomenon for realizing, ultrafast optoelectronic devices because of the very short relaxation time. Above all, the relaxation time of the ISBT in AlGaN-GaN MQWs is theoretically predicted to be 100 fs or shorter, due to strong coupling of electrons with the longitudinal (LO) phonons. In this study, we experimentally demonstrated the ultrafast relaxation process due to ISBT in Al/sub 0.65/Ga/sub 0.35/N-GaN MQWs by a pump-probe measurement. A theoretical fit indicated that the relaxation time is shorter than 150 fs at a wavelength of 4.6 /spl mu/m.