Specific features of transmutational do** of ³⁰Si-enriched silicon crystals with phosphorus: Studies by the method of electron spin resonance

Abstract

Electron spin resonance (ESR) is used to study the neutron transmutation do** of silicon crystals enriched with ³⁰Si isotope: phosphorus donors and radiation defects produced in the course of transmutational do** are observed. The ESR signals related to the phosphorus uncontrolled impurity in ³⁰Si before transmutational do** (the P concentration is ∼10¹⁵ cm⁻³) and phosphorus introduced by neutron irradiation with doses ∼1 × 10¹⁹ cm⁻² and ∼1 × 10²⁰ cm⁻² (the P concentrations are ∼5 × 10¹⁶ and ∼7 × 10¹⁷ cm⁻³, respectively) are studied. As a result of drastic narrowing of the phosphorus ESR lines in ³⁰Si, the intensity of lines increased appreciably, which made it possible to measure the phosphorus concentration in the samples with a small volume (down to 10⁻⁶ mm⁻³). The methods for determining the concentration of P donors from hyperfine structure in the ESR spectra of isolated P atoms, exchange-related pairs, and clusters that consist of three, four, and more P donors are developed. In the region of high concentrations of P donors, in which case the hyperfine structure disappears, the concentration of P donors was estimated from the exchange-narrowed ESR line.