The Si impurity is diffused (850 °C, 10 h,xj∼2.4 &mgr;m) into 2.4 &mgr;m of AlxGa1−xAs‐GaAs (x≳0.6) superlattice (barrierLB≊320 A˚, quantum wellLz≊280 A˚) and disorders it into bulk‐crystal Alx′Ga1‐x′As (x′≳0.32). The as‐grown infrared gap superlattice is converted selectively to red gap bulk crystal and, where undiffused and not disordered, is still capable of continuous 300‐K photopumped laser operation at a threshold of 4×103W/cm2(orJeq∼1.7×103A/cm2, 5145 A˚ pump photon).