Abstract

Recently, optical intersubband (IS) transitions at the communications wavelength of λ. ~ 1.55 µm are studied with growing interest. ^1.2 Ultrafast IS transitions may be able to satisfy the demand for higher speed and bandwidth in optical communications devices. GaN/AIGaN-based heterostructures are of particular interest due to their large band offset, large effective electron mass (m* ~ 0.2-0.3 m₀) and large longitudinal optical phonon energy E_LO ~ 90 meV, leading to IS transitions with ultrafast electron relaxation rates at short wavelengths. Previously, IS scattering times in GaN/ AIGaN multiple quantum wells (MQW) at λ. ~ 4.5 µm wavelength have been measured to be 150 fs.¹ For a MQW sample with a λ. - 1.55 µm IS transition, we recently found a scattering lifetime of 370 fs.²

© 2002 Optical Society of America