Dependence of the AlxGa1−xAs band edge on alloy composition based on the absolute measurement of x

Abstract

The absolute determination of the Al concentration, x, in epitaxial layers of Al_xGa_1−xAs was carried out using a nuclear reaction technique. This technique utilizes the narrow resonances found in the ²⁷Al( p,γ)Si²⁸ reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition. The Al_xGa_1−xAs band edge was measured on these samples through low‐temperature photoluminescence (2 K) measurements. An improved value of the direct edge (Γ) on composition was determined to be E^Γ_g =1.512 +1.455x(eV) within a ±0.3% limit. The direct‐to‐indirect transition was found to occur at an Al concentration of x≂0.37±0.015, lower than previously reported for He temperatures.