RE-EVAPORATION EFFECTS AND OPTICAL-PROPERTIES OF MOLECULAR-BEAM-EPITAXIAL ALGAAS GAAS/ALGAAS WELLS/

Elemental materials that condense on surfaces near effusion cells can be reevaporated toward substrates when heated by radiation from effusi on furnaces. There they accumulate as unwanted impurities at interface s and distribute throughout epitaxial films during growth. This effect is greatly increased when shutters are closed. Re-evaporated aluminum is shown to degrade minority-carrier properties of Al0.3Ga0.7As/GaAs double heterostructures. Modified temperature schedules and hardware t o reduce re-evaporation effects are suggested.