Metastable species of oxygen‐related donors in silicon

Abstract

In the last years, our knowledge about the electronic structure of oxygenrelated donors formed after heat treatment at temperatures between 300 and 500 OC in oxygen-containing silicon, the so called thermal donors, has been greatly enlarged by a successful use of infrared spectroscopic techniques /1 to 4/.Up to now it has been well established that these thermal donors give rise to a series of double donor species with closely spaced ionization energies. For explaining these properties, new microscopic models have been elaborated /5, 6/, assuming the formation of electrically active clusters with increasing number of oxygen atoms to be responsible for the occurrence of the different donor species. Especially in /5/ it was pointed out that in the "starting" phase metastable oxygen complexes would be stabilized by successively captured oxygen atoms. red absorption spectra of the high-energy s e r i e s (D ) of oxygen-related donors in silicon which gives some evidence for the metastable character of donor species in the initial stage of its formation.by appropriate heat treatment at 450 . ' C, thermal donors have been introduced with concentrations of lX1014 cmm3 (sample l), 1~1 0~~ cm-3 (sample 2), and 1. 3x1015 cm-3 (sample 3). Infrared transmission measurements have been carried out with a commercial infrared grating spectrophotometer allowing the sample to be illuminated with polychromatic light with o r without band gap excitation.In this note we report the observation of some unusual behaviour in the infra- +The samples used were boron-doped Czochralski silicon crystals into which,The full curve of Fig. 1 shows a part of the spectrum of the high-energy (D+) series of oxygen-related donors of sample 3 measured at liquid neon temper-1 ) Hausvogteiplatz 5 -7, DDR-1086 Berlin, GDR.

Characterisation of negative-Udefects in semiconductors

“…In Si and Ge crystals containing oxygen-related thermal double donors, significant changes in n(T ) dependencies and IR absorption spectra have been observed after cooling the investigated samples down under external illumination with energy hν ≥ E g [63,20,71,21,72,73,69]. In the 'illuminated' IR absorption spectra of Si crystals, three sets of absorption bands, which have not been seen in the spectra recorded after cooling down in the dark, were detected [20,71,72,73].…”

“…In Si and Ge crystals containing oxygen-related thermal double donors, significant changes in n(T ) dependencies and IR absorption spectra have been observed after cooling the investigated samples down under external illumination with energy hν ≥ E g [63,20,71,21,72,73,69]. In the 'illuminated' IR absorption spectra of Si crystals, three sets of absorption bands, which have not been seen in the spectra recorded after cooling down in the dark, were detected [20,71,72,73]. From the analysis of positions of the electronic-transition related absorption lines in the 'illuminated' spectra, the exact locations of energy levels of three bistable TDD species (negative-U defects) in the shallow donor configuration could be determined in both Si and Ge [20,71,72,73,69].…”

“…In the 'illuminated' IR absorption spectra of Si crystals, three sets of absorption bands, which have not been seen in the spectra recorded after cooling down in the dark, were detected [20,71,72,73]. From the analysis of positions of the electronic-transition related absorption lines in the 'illuminated' spectra, the exact locations of energy levels of three bistable TDD species (negative-U defects) in the shallow donor configuration could be determined in both Si and Ge [20,71,72,73,69].…”

“…In Si and Ge crystals containing oxygen-related thermal double donors, signi cant changes in n(T) dependencies and IR absorption spectra have been observed after cooling the investigated samples down under external illumination with energy hν E g [20,21,63,69,[71][72][73]. In the 'illuminated' Figure 8.…”

“…That way, the triple-peak ne structure with intensity ratio of about 2:3:1 on each band (from high to low frequency peaks), could be explained by a combination of natural occurring Ga isotopes. Considering that 69 Ga and 71 Ga are found in a proportion of about 3:2, a natural population of 69 Ga-X- 69 Ga, 69 Ga-X- 71 Ga, and 71 Ga-X- 71 Ga units corresponds to an intensity ratio of 9 : (2 × 6) : 4 = 2.25 : 3 : 1, respectively [124,125]. Based on sample history arguments and semi-empirical calculations, the X element was suggested to be oxygen [124].…”