Variable-gap $Al_xGa_{1-x}As$ heterostructure for an electron-beam-pumped laser

A variable-gap (graded) heterostructure based on a $p$-type $Al_xGa_{1-x}As$ solid solution was used in a laser pumped transversely by an electron beam. The structure consisted of an $Al_xGa_{1-x}As$ ($x\approx0.2$) buffer layer on a $GaAs$ substrate, an active $GaAs$ layer, and a solidsolution layer of variable composition ($0.1\lesssim x\lesssim0.3$) with the band gap increasing toward the surface. A method was developed for fabricating one layer by forced cooling of a saturated $Ga-Al-As$ molten solution, containing $Si$ as a $p$-type impurity present in a concentration $[p]=(3-5)\times 10^{17}$ cm$^{-3}$, and the other layers by isothermal mixing of two solutions characterized by different $Al$ concentrations. A study was made of the parameters of the finished lasers operating at $T=300$ K.