Defects and Oxygen in Silicon Studied by Positrons

Abstract

During the last few years wide interest is generated in applying the positron annihilation techniques to defects in semiconductors. Since defects in semiconductors are, in many regards, dissimilar to defects in metals one must expect that new responses from positrons will emerge not normally associated with metals. One such important effect would be the charged state of a defect in a semiconductor. At the present time silicon is the semiconductor which has been investigated mostly, but the important 111-V GaAs compound semiconductor is currently also under intensive investigations. For the case of silicon a detailed review will be presented encompassing lifetime results for vacancy agglomerates, high-temperature equilibrium measurements (undoped and P-doped) and oxygen in silicon. Furthermore, indications for the temperature variation of the bulk lifetime and its possible variation with doping levels will also be discussed. Wahrend der vergangenen Jahre konnte einiges Interesse an der Anwendung der Positronen-annihiIationstechnik auf Defekte in Halbleitern geweckt werden. Da Defekte in Halbleitern in vielerlei Hinsicht unterschiedlich zu Defekten in Metallen sind, mu13 man erwarten, da13 man neue ,,Antworten" von Positronen erhalt, die man mit Metallen nicht verbinden wurde. Einer jener wichtigen Effekte ist der Ladungszustand eines Defektes in einem Halbleiter. Zur Zeit ist Silizium der am hiiufigsten untersuchte Halbleiter, doch wird auch am wichtigen III-V-Verbindungshalbleiter GaAs intensiv Porschnng betrieben. Es wird ein detaillierter Uberblick gegeben hinsichtlich des Silizium; er umfaBt Lebensdauerresultate fur Leerstellenagglomerate, Hochtemperaturmessungen im thermischen Gleichgewicht (fur undotiertes und P-dotiertes Si) und Sauerstoff in Silizium. Weiter werden Hinweise auf eine Abhangigkeit der Lebensdauer im defektfreien Kristall von der Temperatur und moglicherweise vom Dotierungsgehalt diskutiert. 31 physica (a) 102/2

Defects and Impurities at the Si/Si(100) Interface Studied with Monoenergetic Positrons

“…The data can also be fitted by our assuming no electric field and a uniform (dilute) concentration of defects in the overlayer (vC = 3x 10 9 ; S D /S B = 1.03), although the X 2 is in this case slightly higher. By use of the specific trapping rate obtained for point defects in silicon by positron lifetime techniques 21,22 (v-3xl0 14 s _1 ), the above implies a defect concentration of C-10 ~~5. Given the systematic limitations of the present experiment (e.g., stopping-profile uncertainties, statistic, etc.…”

Positron annihilation in hydrogen-doped alkali-metal fullerides

“…These lifetimes are shorter than those obtained as an intermediate lifetime component in the present work, which suggests that the defects in hydrogen-doped alkali-metal fullerides are not monovacancy, but higher-order one. The lifetime of positrons in the surface state has been reported to be 0.400 ns for a hydrogenated carbon film [15], 0.45 ns for graphite [16] and longer than 0.520 ns for a 6-vacancy cluster in Si [17]. From these results, it is concluded that hydrogen-doping to alkalimetal fullerides increases the concentration of higher-order vacancy-type defects, through which more than 50% injected positrons annihilate.…”

Defect evolution in Co-implanted Si during annealing at 1000 °C studied using variable-energy positrons and Rutherford backscattering

“…For fluences greater than 6ϫ10 15 cm Ϫ2 , the density of defects 1 and 2 is at least 1ϫ10 19 and 2.5ϫ10 19 cm Ϫ3 , respectively, whereas for 4ϫ10 15 cm Ϫ2 the density of defect 2 falls to 1.5ϫ10 19 cm Ϫ3 . For fluences of 1ϫ10 15 and 2ϫ10 14 cm Ϫ2 , only defect 1 is present at concentrations of 1ϫ10 19 and 2ϫ10 18 cm Ϫ3 , respectively. If there exists a built-in electric field as speculated in Sec.…”