Injection Electroluminescence in (AlxGa1−x)As Diodes of Graded Energy Gap

p‐n junction diodes were made from AlAs‐GaAs mixed crystals of graded composition (energy gap). The energy gap vs composition was determined from measurements of the diode band‐edge emission peaks vs electron microprobe analysis of p‐n junction composition. A linear energy‐gap variation was observed throughout the composition range 0–0.45 mole fraction AlAs. Measurements of the injection‐current dependence and the temperature dependence of the emission spectra of these diodes, interpreted according to a simple model of injection electroluminescence, indicate that the AlAs‐GaAs mixed crystals are of direct band nature to at least 0.25 mole fraction of AlAs. Diodes of 0.40–0.45 mole fraction AlAs junction composition, i.e., in the vicinity of the ``direct‐indirect'' crossover, produced emission which requires more complex analysis.