STEEP DOPING PROFILES OBTAINED BY LOW-ENERGY IMPLANTATION OF ARSENIC IN SILICON MBE LAYERS

Molecular beam epitaxy layers doped by low-energy implantation of arsenic -either during growth or during interruptions of growth (δ-doped layers)- have been characterized with respect to incorporation probability and electrical activity of the implanted arsenic, electron mobility and steepness of the doping profiles. Results show that (1) even at low implantation energy, incorporation probability is equal to unity and all the arsenic atoms are electrically active, (2) bulk mobility is obtained in layers doped during growthj and an interesting mobility enhancement is observed in δ-doped layers and (3) steepness of the doping profiles obtained is beyond the depth resolution of secondary ion mass spectrometry. Simulations of doping profiles indicate that doping gradients of 20 Å per decade should be expected. © 1990.