Influence of deep impurity levels on the threshold characteristics of electronbeam-pumped lasers made of $n-Ga_{1-x}Al_xAs$

A study was made of the threshold characteristics of $Ga_{1-x}Al_xAs$ lasers pumped by an electron beam. The study was carried out in a wide range of compositions ($0.10\lesssim x\lesssim0.30$) and of the degree of doping ($5\times10^{16}$ cm$^{-3}\le n\le1\times10^{18}$ cm $^{-3}$). The nature of the dependence of the threshold current density on the composition and on the degree of doping was accounted for by considering the nonradiative recombination process associated with deep donor levels characterized by an activation energy $E_\alpha=150$ meV relative to the $L$ minimum of the conduction band and by a nonradiative recombination cross section $\sigma= (1.8-2.0)\times 10^{-17}$ cm$^2$. The optimal values of the degree of doping were determined for various compositions.