It is shown by dielectric resonance absorption at 60 GHz that there is a linear coupling of the electric field to the ground state of effective mass acceptors in Si reflecting the lower Td symmetry in the central portion of the ground state wave function. The couphng increases strongly with increasing binding energy from B to In, i.e., with decreasing Bohr radius of the ax:ceptor. An unexpected nonlinear Zeeman splitting is observed the magnitude of which also increases from B to In. For all acceptors a central fine structure is found which correlates with the homogeneous line width.PACS numbers: 7L55.Ht, 71.70.Ej Linear coupling of an electric field to the fourfold degenerate Fs acceptor ground state in silicon or germanium is forbidden within the effective mass approximation (EMA) by inversion symmetry. However, it becomes possible by the local Ta symmetry of the central cell [1,2] and should therefore be stronger for deeper acceptors with more localized envelope functions. An experimental verification of this linear coupling can be made by measuring the strength of electric dipole resonance transitions between ground state levels split by a magnetic field. For such an experiment, high quality samples are essential: In the first EPR investigations of acceptors in Si at 10 GHz [3], the magnetic ±1/2 transition was observable only under high enough uniaxial stress to override the level mixing of the Fg quartet inhomogeneously broadened by internal strains. Later, separate lines in Si:B samples could be resolved at zero stress by EPR at 10 GHz [4] and APR (acoustic paramagnetic resonance) [5]. However, the appearance of a relatively strong forbidden Am = 3 transition showed that the random strain splitting was not small enough as compared to the magnetic field splitting at 10 GHz for an absolute determination of the strength of the electric dipolar transition. We have, therefore, designed our experiment at 60 GHz using samples with small inhomogeneous broadening according to previous ultreisonic measurements [5][6][7][8].The interaction Hamiltonians for elastic, electric, and magnetic perturbations have been summarized in [2] on the basis of group theoretical considerations together with estimates for the coupling constants. The matrix elements for elastic and electric perturbations of the Fg state with its substates with magnetic quantum numbers rrij -3/2, 1/2, -1/2, and -3/2 (indexed 1, 2, 3, and 4, respectively) can be written as follows [5]:if 11 = -H22 = -Hs3 = if44 = Ai ,where the A^ are given by the elastic (e) and electric (E) fields and the corresponding coupling constants:b' and d' are the two deformation potential constants. (3' and 6' are the two coupling constants for the quadratic Stark effect and peff is the effective electric dipole moment for linear Stark coupling. Peff is zero for inversion symmetry, i.e., for the acceptor ground state as calculated within the EMA. E is the externally applied electric field including the effect of a local field [9]. PeflF is a measure of the probability density o...

The "spin"-lattice relaxation of the two-level system of the strain-split acceptor ground state of Si(B) is determined from the temperature dependence of the ultrasonic relaxation attenuation, around 10 K. It is found that Raman relaxation alone does not fit the results but that, in addition, an Arrhenius-type of relaxation, possibly due to a Jahn-Teller effect, is involved. The transverse relaxation is obtained from intensity-dependent and hole-burning measurements of the resonant attenuation. At small acceptor concentrations it is determined by "spin"-lattice relaxation alone ; for higher concentrations an additional temperature-independent interaction term is found much smaller than expected for elastic dipole or exchange interaction.Die ,,Spin"-Gitter-Relaxation des Zweiniveausystems des Akzeptorgrundzustandes von Si(B) wird durch Messung der Ultraschallrelaxation im Bereich um 10 K untenucht. Ramanprozesse allein reichen zur Beschreibung der Resultate nicht Bus. Es ist noch eine Arrhenius-Relaxation beteiligt, die wir dem Jahn-Teller-Effekt zuschreiben. Die transversale Relaxation wird aus intensitatsabhangigen und hole-burning-Meseungen der Resonanzdimpfung bestimmt. Bei kleinen Azeptorkonzentrationen ist die ,,Spin"-Gitter-Relaxation allein mal3gebend; bei hoheren Konzentrationen kommt ein temperaturunabhingiger Wechselwirkungsterm hinzu, der aber kleiner ist, als es fur elastische Dipol-oder Austauschwechselwirkung erwartet wird.

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Comparative phonon emission experiments carries out in liquid helium and vacuum with superconducting tin-tin tunneling junctions evaporated on silicon crystals, show a transmission into helium about three times higher than the transmission into silicon.In phonon generation and detection experiments with superconducting tunneling junctions [l] it is possible to determine the number of 2A phonons generated (corresponding to 280 GHz for tin) as well as the absolute sensitivity of a junction when used as a phonon detector.Using an acoustic model of the photon radiation into the substrate, the rate of phonons to be detected can be calculated and compared with the experimental value. This permits conclusions to be drawn on phonon losses which may occur by emission into the helium bath or by thermalisation within the generator detector system _ In a superconducting junction biased at U, = 2A/e, pair breaking and recombination results in the generation of one 2A phonon per tunneling electron. The generation rate of 2A phonons is therefore (Jc = generator current) ri, = JG/e .(1)On the other hand, 2A phonons being absorbed in the detector by pair breaking at a rate r&, cause a stationary change 6iV in quasiparticle concentration[2]where rexp is the experimental recombination lifetime as determined from pulse decay measurements which is enhanced ever the true recombination lifetime because of recombination phonon reabsorption by Pair breaking [3] ; 7exp depends on the junction thickness and the phonon escape probability into the adjacent crystal and the helium. The change of the quasiparticle concentration 6N can be obtained absolutely from the detector short circuit signal current by calibration with the thermal quasiparticle tunneling current.The detected phonon rate nD as obtained from eq. (2) is to be compared with a detected phonon rate calculated from tic using the following model:1. Emission of all primarily generated 2A phonons into the crystal with Lambert's cosine law corrected for phonon focusing [4] and phonon reflection at the crystal-detector interface.2. re2-dependence of the phonon intensity. show that nD,exp Ii D talc < 1 under all conditions even under vacuum condiiions. This discrepancy indicates phonon losses possibly by: phonon interaction with phonons, quasiparticles and defects; generation of surface phonons an% thermalisation at interfaces; incomplete absorption inside the detector.Comparing nD,exp/nD,c,rc for liquid helium with nDgxp/'iD talc under vacuum conditions, we find an increase by a factor 3.8. The same increase ratio is obtained for rexp (1900 nsec/.500 nsec). It can be shown that in vacuum the rate of phonons detected 'iD should increase in the same way as rexp of the generator. Since our detector signal S a n in agreement with the experimental values Tvac/THe = 3.8; S,,ac/SHe = l4 .To compare the transmission into helium with the transmission into the silicon crystal, we calculated the dependence of ren on the junction thickness d [6] for the dominant transverse wave contribution.Ford...

The splitting distribution of the acceptor ground state of Si(B) is determined from the frequency dependence of the ultrasonic resonance attenuation and from acoustic paramagnetic resonance. In the purest crystals a residual distribution is found of unknown origin. In crystals containing carbon or oxygen at concentrations above about 10z2 m-s the distribution is broadened in rough accordance with statistical estimates.Die Aufspaltungsverteilung des Akzeptorgrundzustandes von Si( B) wird aus der Frequenzabhgngigkeit der Ultraschalldlmpfung und aus der akustiachen paramagnetischen Resonanz ermittelt I n den reinsten Kristallen wird eine restliche Verteilung unbekannter Herkunft gefunden. In Kristallen mit Kohlenstoff und Sauerstoff in Konzentrationen oberhalb etwa loz2 m-3 ist die Vertailung verbreitert in ungefahrer Ubereinstimmung mit statistischen Abschatzungen. 1) D-7000 Stuttgart, FRG. 2) Part I see phys. stat. sol. (b) 111, 213 (1982). 36 *