Properties of high-purity AlxGa1-xAs grown by the metalorganic vapor-phase-epitaxy technique using methyl precursors
Abstract
The metalorganic vapor-phase epitaxy (MOVPE) of AlxGa 1-xAs most commonly employs the methyl precursors Al(CH 3)3 and Ga(CH3)3. These precursors were used in the growth of AlxGa1-xAs over the entire range of alloy composition in a low-pressure horizontal MOVPE reactor. A complete chemical, electrical, and optical characterization of high-purity MOVPE AlxGa1-xAs grown over the entire range of growth temperatures (600-800 °C) was carried out in order to determine the relationship of the materials properties to the growth conditions. Carbon, the primary impurity in the layers, dominates the electrical properties of the epitaxial layers. A superlinear dependence of carbon incorporation on AlAs mole fraction is observed, along with a two-slope dependence on growth temperature. Photoluminescence spectra (2 K) were obtained from materials with AlAs mole fraction over the range 0≤x≤0.80. The photoluminescence intensity of the layers also exhibits a systematic dependence on alloy composition and growth temperature. The in situ gettering of oxygen by the growth reactants is necessary to achieve high luminescence intensity and low electrical compensation. The influence of the reactor design on this gettering process is modeled.