  We describe the influence of hard wall confinement and lateral dimension on
the low temperature transport properties of long diffusive channels and
ballistic crosses fabricated in an InSb/InxAl1-xSb heterostructure. Partially
diffuse boundary scattering is found to play a crucial role in the electron
dynamics of ballistic crosses and substantially enhance the negative bend
resistance. Experimental observations are supported by simulations using a
classical billiard ball model for which good agreement is found when diffuse
boundary scattering is included.
