Abstract
For the first time, a quantitative model of the Curie–Weiss behavior of a low-temperature paramagnetic susceptibility of electrically neutral donors in n-type diamagnetic covalent semiconductors is proposed. The exchange interaction between nearest two neutral donors was calculated with the use of the Heitler–London model. In this model, we take into account the change in the thermal ionization energy of donors due to the shift of the bottom of the conduction band to the bandgap with doping and compensation. The energy of the exchange spin–spin interaction between electrons localized on donors is calculated as a function of the donor concentration and the degree of their compensation by acceptors. The broadening of the donor band due to the Coulomb interaction of the nearest impurity ions was taken into account. We considered crystals of n-type germanium doped with arsenic up to the concentration close to the insulator–metal phase transition (Mott transition) and compensated with gallium. The compensation ratio K is the ratio of the concentration of compensating acceptors KN to the concentration of doping donors N. The model predicts a change in the sign of the Curie–Weiss temperature from minus to plus (a transition from the antiferromagnetic to ferromagnetic local ordering of electron spins on donors) for K ≈ 0.15–0.3, reaching its maximum positive values of ≈1.3 K for K ≈ 0.5 with the following decrease (a transition to paramagnetism) for K > 0.85. The calculated behavior of the paramagnetic susceptibility of donors is consistent with the experimental data for compensated n-Ge:As,Ga samples close to the Mott transition.
Highlights
Despite the more than half a century history of study of the electron spin resonance (ESR) of hydrogen-like impurities in covalent semiconductor crystals, beginning with the work of Wilson,1 this subject still attracts much attention
A number of studies2–5 were devoted to the low-temperature6 magnetic susceptibility of crystalline semiconductors doped with hydrogen-like donors under the conditions of interaction of electron spins localized on donors, in particular on the insulator side of the concentration insulator–metal phase transition (Mott transition)
It has been shown by ESR spectroscopy that in semiconductor crystals close to the Mott transition electrons with oppositely directed spins, which are weakly localized on the nearest impurities, may form the so-called antiferromagnetic spin glass. (On the other hand, the existence of the magnetic ordering in semiconductor materials and structures doped with shallow impurities is scitation.org/journal/adv supported experimentally with the use of methods different from ESR.8,9)
Summary
Despite the more than half a century history of study of the electron spin resonance (ESR) of hydrogen-like (shallow) impurities in covalent semiconductor crystals, beginning with the work of Wilson, this subject still attracts much attention. We propose a model for the transition from the antiferromagnetic ordering of electron spins of shallow paramagnetic impurities (donors) to the ferromagnetic ordering This transition is affected by internal (doping level and degree of compensation) and external (temperature and magnetic field) factors. Where N0 = N0↑ + N0↓ = (1 − K)N is the concentration of donors in the charge state (0) at low temperatures, gd ≈ 1.57 is the g-factor of an electron of the hydrogen-like donor impurity of arsenic in the germanium crystal, which is not involved in the covalent chemical bonding, B0 = 425 mT is the induction of the external constant magnetic field used in ESR experiments in Refs. We discuss main results using the predictions of the proposed model to be compared with the experimental data on the n-Ge:As doped up to the metal–insulator phase transition and compensated by Ga acceptor impurities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
