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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.

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