Excitation Spectra and Piezospectroscopic Effects of Magnesium Donors in Silicon

Abstract

Excitation spectra of magnesium impurities diffused into undoped silicon as well as into silicon doped with group-III acceptors have been measured. In the former, magnesium is a heliumlike neutral donor (Mg ) with excited states similar to those of group-V donors and close to the effective-mass positions; its ionization energy at liquid-helium temperature is 107.50 +0.04 meV. In specimens containing group-III impurities, with the magnesium partially compensated, excitation spectra are observed similar to those of group-V donors and that of Mg except that the spacings between corresponding lines are approximately four times larger and the 1s(hl) -2p~t ransition is a closely spaced doublet, 0. 2 meV apart. These features are consistent with a singly ionized heliumlike magnesium donor (Mg') and a small chemical splitting of the 2p~state; the ionization energy is 256. 47+0. 07 meV at liquidhelium temperature.The excitation spectrum of Mg' was also observed in specimens containing Mg subjected to high-energy electron irradiation. Study of the piezospectroscopic effects shows that both Mg and Mg' occupy a 7&-symmetry site with ls(A. &) as the ground state. A value of 8. 7 +0.2 eV has been deduced for the shear-deformation-potential constant -"of the (100) conduction-band minima of silicon.

Dynamics of nonequilibrium electrons on neutral center states of interstitial magnesium donors in silicon

“…Because of this uncertainty one cannot exclude an intermediate case between the single-phonon relaxation scheme (assuming the binding energy of the lowest excited state to be 52.5 ± 3 meV [1]) and the two-phonon relaxation scheme, if the binding energy of the lowest excited state is ≈ 33 meV (common to all other donors) [7]. Two-phonon interactions in silicon give rise to dominant bands in lattice absorption spectra [8] as well as in Raman spectra of Si [9].…”

“…The so-called "chemical shift" of a neutral Mg 0 donor, i.e., the downshifting of the impurity ground state relative to its position as derived from effective mass theory [1], is larger than the group-V donors in Si. This makes magnesium in Si a transition case between the shallow donors in Si, where singleintervalley-phonon-assisted transitions dominate intracenter relaxation [2,3], and the deeper, heliumlike group-VI donors in Si, where electron capture into the ground state can be assisted only by multiphonon interactions [4].…”

“…Magnesium (Mg, group-IIA) atoms in interstitial positions of a silicon (Si) host lattice form double donor centers with a binding energy E i in the neutral Mg 0 state of ∼107 meV [1]. The so-called "chemical shift" of a neutral Mg 0 donor, i.e., the downshifting of the impurity ground state relative to its position as derived from effective mass theory [1], is larger than the group-V donors in Si.…”

Диффузия Межузельного Магния В Бездислокационном Кремнии

“…Поэтому инте-ресна перспектива использовать для этих целей также и примесь магния [3]. Для получения Si : Mg приме-нялись различные методы: выращивание кристаллов из расплава [4], диффузия из газовой фазы в запаянной ампуле [5], жидкофазная эпитаксия [6], так называемый " сандвич-метод" (sandwich diffusion technique) [7][8][9], а также ионная имплантация [10]. В работе [11] легирова-ние кремния осуществлялось путем напыления пленки магния на поверхность образца с последующей обра-боткой образца импульсным лазерным излучением и высокотемпературным прогревом.…”

“…Исследования электронного парамагнитного резонан-са (ЭПР) Si : Mg и результаты спектроскопии погло-щения в инфракрасной (ИК) области [7,8] показали, что в межузельных положениях (состояния Mg i ) при-месь является двойным донором с уровнями энергии E c − 0.11 и E c − 0.25 эВ. При этом, как следует из измерений проводимости, Mg i имеет очень низкую рас-творимость (∼ 10 15 см −3 ).…”