DONOR ACTIVATION AND ELECTRONIC SCREENING AT AN ANTIMONY DELTA-LAYER IN SILICON

Electron spectroscopic studies of highly concentrated delta layers of Sb impurity atoms in epitaxially grown Si(001) have revealed the prese nce of two main Sb environments. An analysis of the kinetic energies o f the core-level photoemission and Auger spectra of Sb in terms of the Auger parameter shows that the core holes on each sire-are less well screened than in the purl element. A simultaneous analysis of shifts i n the initial-state and final-state Anger parameters of the two sits a nd bulk Sb enables one site to be identified with positively charged d onors, and the other with neutral Sb, possibly in clusters, defects, o r interstitial sites. The donors are found to contribute between 0.12 add 0.20 electrons per Sb atom, in agreement with transport measuremen ts on similarly prepared specimens. The on-site screening of core hole s on the two sites, dq/dN, is found to be 0.82 and 0.93 For the delta( 1) and delta(2) sites, respectively. This result is consistent with th e expectation that the donor site will be better screened by access to the electron gas of donated electrons.