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Electron microscopy images from heterostructures of GaAs/AlGaAs have been studied with focus on high resolution and microstructure. Cross-section investigations of 100 direction off axis growth show approximately constant layer thickness in the area studied. The AlGaAs-layers are on the average 22 +/3 A and the GaAs-layers 78 +/-3 A. The off-axis angle is found to be 2.5 deg. No interface steps are observed. This is due to the direction of the steps which makes it impossible to see the steps edge on. Threading dislocations, stacking faults and microtwins are observed in hetero-structures grown on patterned surfaces. Close to positions of abrupt changes in layer direction near the sidewalls of the grooves, the favored planes are (411) both for growth at low (630 C) and high (715 C) temperature substrates.