CARRIER DISTRIBUTION IN QUANTUM-WELL LASERS

We have studied the balance of charge between two wells of different width placed asymmetrically in the same waveguide of a double quantum well laser diode structure. Pure spontaneous emission spectra have been measured from 40 and 80 angstrom wells over a range of temperatures from 80 to 290 K. We have studied the charge distribution between these wells by determining the difference in the Fermi level separations (DELTA) in the two wells using a method based on relationships between spontaneous emission and absorption. The value of DELTA tends to the difference in the lowest energy level separation in the two wells as the temperature is reduced. Below approximately 150 K the temperature dependence of DELTA depends upon the relative position of the wells across the waveguide. The data are discussed in terms of carrier capture and mobility.