Electron Spin Resonance Experiments on Shallow Donors in Germanium

Abstract

of 2.20 ±0.02 ev with a half-width of a few kT. This value is a few hundredths of an electron volt lower than the peak obtained from the van Roosbroeck-Shockley theory 2 using the calculated a's (derived from the Macfar lane-Roberts analysis), but agrees well with the peak obtained using the above-discussed additional low-energy absorption. It is interesting to note that a comparison of the high-energy side of the spectral curve of electroluminous emittance to the van Roosbroeck-Shockley theory indicates a photon travel through GaP of about 10 " 2 cm. This is in rather good agreement with the value obtained from the photocurrent vs hv analysis. Some of the additional lovf-hv emission is most likely due to defect sites mentioned above. These and self-absorption cause the peak to shift somewhat to lower energies.We conclude that most of the electroluminescent phenomena on hand are quite distinct from those originating from recombinations via defect states as reported previously. 1 ' 12 In all the latter cases the photon distribution peaks at energies lower than the energy gap value obtained from free carrier recombination electroluminescence reported in this Letter, or from the analysis of other optical data. Also in all defect center recombination cases a linear dependence of the light on current has been found. The agreement between the above-discussed characteristics of electroluminescence, optical absorption, and photoelectric response leads us to identify the electroluminescent phenomenon as one primarily due to band-to-band bimolecular transitions.We have also seen bimolecular recombination kinetics for radiative transitions of carriers injected across a rectifying junction in indium phosphide. Braunstein 5 reported the presence of Electron spin resonances on shallow donors in silicon have been studied by several authors. 1 " 3 In germanium there are various factors which make the observation of electron spin resonance signals more difficult and, so far, no resonances have been reported on shallow impurity states. The recent conflicting experimental results pertaining to the donor ground state in germanium 4 ' 5 recombination radiation in InP at an energy close to the band gap. We have obtained the spectral distribution of this radiation. It is shown in Fig. 2. The position of the peak at 1.25 ev is in good agreement with the band gap values reported in the literature. 13 The authors wish to express thanks to R. Braunstein, A. R. Moore, and J. I. Pankove for helpful discussions.led us to reinvestigate the electron spin resonance behavior in this material. In the present Letter we wish to report on the observation of electron spin resonances from both bound and nonlocalized electrons in germanium. The results indicate that the ground state of the arsenic and phosphorus donors in germanium is a singlet.

Progress towards Spin-Based Light Emission in Group IV Semiconductors

“…The ensemble spin coherence time of electrons was pointed out to exceed 1 ns and to be constant for a wide range of carrier densities and for temperatures up to 60 K [131]. The effective electron g-factor for bulk Ge was inferred to be about 1.83 [131], in reasonable agreement with available electron spin resonance data and theoretical predictions [134,135].…”

Intrinsic spin lifetime of conduction electrons in germanium

“…34 Theoretical efforts in the early days 35,36 were motivated by low-temperature electron spin resonance experiments that studied the g factor and spin-lattice relaxation of localized electrons in donor states. [37][38][39] On the other hand, little attention was paid to conduction electrons whose spin relaxation is mediated by the Elliott-Yafet mechanism. 40,41 By analyzing the space inversion and time reversal symmetries of the L point, Yafet deduced a T 7/2 temperature dependence of the spin relaxation rate due to intravalley electron scattering with acoustic phonons.…”

Fast Nuclear Spin Hyperpolarization of Phosphorus in Silicon

“…Dynamic nuclear polarization using off-resonance radiation has been studied extensively 4,6 . Complex pulses or adiabatic passage effects may be used to manipulate spin states, leading to large polarizations 7,8 . Electrical injection of hot carriers has been used to obtain positive polarizations 9 , however this requires electrical contact to the sample.…”