Abstract

Laser diodes incorporating GaAsSb/InGaAs layers in a type-II band alignment have generated much interest due to their optical transitions occurring at longer wavelengths than the bandgap of the constituent layers. We present experimental results of the modal gain and recombination currents of a GaAsSb /InGaAs type-II quantum well laser structure emitting at 1.3 um as a function of current injection and temperature. The system provides a maximum modal gain of 18 cm⁻¹ from the n = 1 transition despite an electron-hole overlap of 32 %. However, gain from the n = 2 transition becomes dominant before this value can be achieved and shifts the peak gain to a shorter wavelength. This limits the usable gain from the long wavelength n = 1 transition and increases the total radiative current. Through analysis of the radiative efficiency at different temperatures we believe that there are two non-radiative processes present that affect performance: the first is due to a defect state associated to the 1HH level and the second due to the population of an unconfined electron level in the GaAs core region. Energy-level calculations are used to discuss potential improvements to a type-II structure emitting at 1300 nm.

© 2007 IEEE