250 AA spacer GaAs/AlGaAs two dimensional electron gas (2DEG) structures with mobilities in excess of 3x10/sup 6/ cm/sup 2/V-1/sub S/-1 at 4 K

摘要

The authors refine the growth procedures to optimise the mobility in a GaAs/AlGaAs 2DEG. A 'standardised' 250 AA spacer structure has been selected for study to allow growth related effects to be identified. Part of the work has been motivated by the observation that with the Si dopant cell operating at high temperatures (<1325 degrees C) there is a noticeable degradation in the As stale RHEED pattern of GaAs. The Si furnace is the hottest section of the MBE system and may be a substantial source of impurities. The effect of a hot, shuttered Si cell on 10 mu m undoped GaAs layers and on 2DEGs has been investigated.