Process for controlling dopant diffusion in a semiconductor layer and semiconductor layer formed thereby

A semiconductor layer comprising:

• a first semiconductor region having diffusion-suppressing, electrically inactive impurity incorporated therein by at least one first crystal growth technique;
• and,
• a second semiconductor region formed on said first semiconductor region by at least one second crystal growth technique, said second semiconductive region being substantially free of electrically inactive impurities and having dopant atoms incorporated therein to a depth not exceeding about 20,000 .ANG.;
• wherein said electrically inactive impurity of said first region is operational to block diffusion of said dopant atoms from said second region into said first region.