SUBNANOMETER ANALYSIS AND MODELING OF MBE GROWN INP BASED MODFETS

InGaAs/InAlAs double-doped double-strained modulation-doped field-effe ct transistors (3D-SMODFETs)(1) were grown by solid source molecular b eam epitaxy. The structures were characterized using high resolution x -ray diffraction, Hall effect, and cross-sectional scanning tunneling microscopy. A record two-dimensional electron gas (2DEG) sheet density of 8.5 x 10(12)/cm(2) and 8.1 x 10(12)/cm(2) for 300 and 77K, respect ively, was achieved. The mobility was 6500 and 12000 cm(2)/ Vs for 300 and 77K, respectively. To the author's knowledge,(2) the previous rec ord 2DEG result was 6.58 x 10(12)/cm(2). The electron mobility was lim ited by alloy scattering and interface roughness caused by the presenc e of ''clustering.'' Using cross-sectional scanning tunneling microsco py to verify the presence of these clusters, we have the first images of the lattice matched InAlAs (spacer)-InGaAs (quantum well) interface . These images reveal clusters that have approximate spherical or cyli ndrical shapes with equivalent cubic dimensions ranging from 25 to 45 Angstrom.