Electroluminescent shifting-peak spectra in GaAs with uniform excitation

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Abstract
Steady‐state and time‐resolved spectra have been measured at room temperature for spontaneous emission from the GaAs active layer of a double‐heterostructure laser. The closely compensated p‐type active layer was heavily doped with Si. The double heterostructure provides carrier confinement and permits observation of spontaneous emission for conditions of uniform excitation. The emission at low levels of excitation was stationary in energy while increasing in intensity. At high levels of excitation, the emission shifts to higher energy while increasing in intensity. These spectra result from radiative recombination in which the injected electrons fill the empty conduction band tails and have been designated here as emission due to the band‐filling mechanism. Equivalence between steady‐state and time‐resolved spectra demonstrated that quasiequilibrium exists within the conduction and valence bands. Carrier distributions and emission spectra were calculated as a function of excitation for valence and conduction band density of states represented by Kane's Gaussian band tails. These calculations showed that the emission for the band‐filling mechanism was stationary in energy as the injected electrons filled the conduction band tails. As the tail states were filled, the low‐energy emission began to saturate and the emission shifted to higher energy. This emission for band filling is compared with the properties of radiative tunneling.