SI SIGE MODULATION-DOPED STRUCTURES WITH THIN BUFFER LAYERS - EFFECT OF SUBSTRATE ORIENTATION/

High quality Si (strained)/Si0.7Ge0.3 (relaxed) modulation-doped struc tures incorporating unusually thin (700 nm) buffer layers were grown w ith molecular beam epitaxy at 700-degrees-C. By utilizing (100) substr ates misoriented toward (011) by 4-degrees, the density of threading d islocations was reduced by over an order of magnitude as compared with conventional techniques. These layers produced exceptionally high Hal l mobilities of 1790 cm2/V s at 300 K and 19 000 cm2/V s at 77 K on n- type modulation-doped heterostructures. The effect of substrate misori entation on threading dislocation density was investigated using trans mission electron microscopy and Nomarski microscopy.