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 scatter
ing 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.
