Sharp profiles with high and low doping levels in silicon grown by molecular beam epitaxy

Abstract
We find that heavy adsorbed dopant layers, up to several tens of equivalent monolayers, can be made to produce heavily doped n (Sb) and p (Ga) layers in molecular beam epitaxy grown silicon. By preadjusting the adlayer concentration to the required value while temporarily arresting silicon growth, arbitrarily sharp profiles of any sequence of dopant type with very high or low levels can be grown. Examples are given of p+ i p+ and n++p+ pp+ structures grown with transition thickness L?300 Å, and with controlled layer thicknesses of ∼1000 Å. Such structures, difficult to achieve otherwise, should be ideal for fabrication of high-frequency millimeter wave devices.