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1.
Measurements of threshold-current density and incremental efficiency on homostructure and heterostructure GaAs lasers show an increasingly superlinear dependence of gaing on current densityJ with increasing temperature. The indexn in the relationg propto J^{n} satisfies the relationn = [1 + (kT/E_{t})^{2}]^{1/2} where Et is a measure of the band-tail depth. 相似文献
2.
We have studied multiple-photon transition in a low-field nuclear magnetic resonance (NMR) experiment. It is well known that a saturation of the NMR occurs when using a sufficiently high alternating magnetic field which induces multiple-photons transitions. We show theoretically that these multiphoton transitions are accompanied by an harmonic generation. For an -photon transition, this generation occurs mostly on then th and (n pm 1 )th harmonic. For an irradiating field2H_{1} cos omega t of pulsation ω such thatnomega= gamma H_{0}=omega_{0} where H0 is the steady field and θ is the angle between H0 and H1 the amplitudesSmin{n}max{n} andSmin{n}max{n+1} of these components are given bySmin{n}max{n} = f_{n}(theta) (H_{1})^{n} ,Smin{n}max{n+1} = cos theta f_{n}(theta) (H_{1})^{n+1} . We have verified these equations in a low-field NMR experiment (H_{0} = 0.7 Gs/s), polarizing first a flowing liquid in a high magnetic field. The liquid then flows in a modified Bloch spectrometer. The receiving coil is still perpendicular to the steady field but it is possible to adjust the angle θ between the axis of the emission coils (H1 field) and the steady-field H0 . Using a synchronous detection at the output of the receiving coil on the pulsation(n - 1) omega, nomega , or(n + 1) omega , we have directly detected multiphoton transistions. The above equations have been verified forn = 2 ton = 5 . There are slight discrepancies at high excitation which may be explained taking into account a large saturation. 相似文献
3.
《Electron Devices, IEEE Transactions on》1986,33(3):391-401
Distributed series resistance effects in solar cells are analyzed and the correctness of representing these by a lumped parameter is discussed for any conditions of bias and illumination. In addition to a general mathematical methodology, analytical expressions are derived to simplify the estimation of series resistance effects on the dark and illuminatedJ-V characteristics of the cell. The equivalent series resistance (rs ) in the dark is found to decrease with current densityJ fromr_{b} + r_{e}/3 at smallJ to (r_{e} r_{b})^{1/2} at very highJ , where re and rb are the emitter layer and base region resistances, respectively. For illuminated conditions rs depends onJ as well, being maximum near short-circuit and minimum near open-circuit; however, rs further depends on the photogenerated current JL : its short-circuit value increases with JL fromr_{b} + r_{e}/3 tor_{b} + r_{e}/2 and the open-circuit value decreases with JL fromr_{b} + r_{e}/3 to(r_{e}r_{b})^{1/2} . The variability of rs is therefore related to the relative importance of rb andr_{e};r_{b} plays the role of attenuating this variability, a situation not well recognized previously. Previous theoretical and experimental work is critically reviewed throughout this paper. 相似文献
4.
《Electron Devices, IEEE Transactions on》1973,20(7):642-647
The influence of As surface concentration CSE on the emitter efficiency βγ and the temperature dependence of βγ are reported. The theoretical model that is used to explain the variation of βγ with CSE is based upon the difference in the effective energy bandgaps in the emitter and base regionsDeltaE_{g} . Experimental measurements ofDeltaE_{g} versus CSE are presented. Measurements of βγ versus CSE show that the effective emitter doping densityQ_{E}/x_{eb} reaches a maximum value atC_{SE} cong 1.5 times 10^{20} atoms/cm3, corresponding to the threshold above whichDeltaE_{g} > 0 . For the case of a constant active base doping/cm2QB , this also corresponds to an optimum in the emitter efficiency βγ . However, it is shown that in typical sequential diffusion processing of transistors, βγ increases monotonically with CSE becauseQ_{B} = Q_{B}(C_{SE}) decreases. In addition, for devices fabricated in this study,Deltabeta_{gamma}/DeltaC_{SE} atC_{SE}=2 times 10^{20} atoms/ cm3for As-diffused emitters (doped oxide) was ≈ 5 times greater than for ion-implanted-diffused As emitters, showing the superiority of implantation in controlling gain. Finally, transistors that were made withC_{SE} siml 1.4 times 10^{20} atoms/cm3(DeltaE_{g} = 0 ) showed βgamma (85°C)/ βγ (-15°C) ≤ 1.05. 相似文献
5.
《Electron Devices, IEEE Transactions on》1982,29(6):965-970
It is found that equivalent gate noise power for l/f noise in n-channel silicon-gate MOS transistors at near zero drain voltage at room temperature is empirically described by two noise terms, which vary asK_{1}(q/C_{ox}) (V_{G} -V_{T})/f and K_{2}(q/C_{ox})^{2}/f, where V_{G} is gate voltage, VT is threshold Voltage, and Cox is gate-oxide capacitance per unit area. Unification of carrier-density fluctuation (McWhorter's model)and mobility fluctuation (Hooge's model) can account for the experimental data. The comparison between the theory and experiment shows that the carrier fluctuation term K2 is proportional to oxide-trap density at Fermi-level. The mobility fluctuation term K1 is correlated to K2 , being proportional toradic K_{2} . The origin of this correlation is yet to be clarified. 相似文献
6.
《Electron Devices, IEEE Transactions on》1957,4(1):22-24
An approximate formula is developed for the current of a parallel-plane diode including the effects of initial velocities of emission. For an oxide-coated cathode (T = 1000 °K) the approximate result is:J = 2.33 times 10^{-6} frac{V^{3/2}}{x^{2}} cdot[1 + frac{11.4(J_{s}x^{2})^{1/4}}{V^{3/4}} + frac{3.22(J_{s}x^{2})^{1/8}}{V^{3/2}}] where,J , Js , andx are in suitable units such that Jx2andJ_{s}x^{2} are in amperes and V in volts. A comparison is made between this result, Child's 3/2 power solution, and the Epstein-Fry-Langmuir solution. The result given above being an explicit solution of the current is particularly advantageous over prior approximate solutions. 相似文献
7.
《Electron Device Letters, IEEE》1985,6(9):450-452
The n-channel LDD MOSFET lifetime is observed to followtau=(A/I_{d})(I_{sub}/I_{d})^{-n} from 77 to 295 K when the device is stressed near the maximum Isub . Here Id is the drain current andA is the proportionality constant. The experimental result indicates thatn is approximately 2.7 and is independent of temperature. However, the proportionality constantA followsA = A_{0} exp (-E_{a}/kT) , withE_{a} = 39 meV. The smaller proportionality constant at low temperatures suggests that hot-electron injection (HEI) degradation is caused by the electron trapping in the oxide. 相似文献
8.
The effects of stimulated Raman scattering (SRS) and of infrared (IR) absorption on the scattering at defects leading to atomic migration in solids is evaluated in detail for certain systems.DeltaE/kT approx sum u_{ic}^{2}/langleu_{i}u_{i}rangle , whereDeltaE is the activation energy, uic is the many-body critical displacement in a migration event, andlangleu_{i}u_{i}rangle is the equal-time correlation function including anharmonic terms. Using the equal-time correlation for the defect lattice in the harmonic approximation, we getDeltaE/kT_{eff} propto 1/sum h[2(n_{s} + n_{e}) + 1] where Teff includes both ne and ns the externally and thermally excited phonon numbers, respectively. The phonon rate density required for an observable effect of SRS or IR absorption on diffusion in solids isn_{e}^{(c)}c_{s}/V approx 10^{26} - 10^{27} phonons/s.cm2, wheren_{e}^{(c)} is a critical number of high wave-vector laser-stimulated phonons, cs , is the sound velocity, and V, the volume per atom. In KCI at 110 K, theory shows thatn_{e} = 0.2 can produce a factor of 10 effect on the reorientation of Na:FA centers. Anharmonic effects onlangleu_{i}u_{i}rangle were calculated and numerical estimates indicate that they would be experimentally observable for large ne . It is found that some of the effects reported here probably contribute, in part, to the permanent damage tracks caused by high-power laser beams in solids and provide an internal source for the initiation of microcracks. In addition, the direction of the stimulated phonon wave vector is shown to produce a directional effect in the control of atomic migration. 相似文献
9.
Multiplication noise in uniform avalanche diodes 总被引:6,自引:0,他引:6
《Electron Devices, IEEE Transactions on》1966,13(1):164-168
A general expression is derived from which the spectral density of the noise generated in a uniformly multiplying p-n junction can be calculated for any distribution of injected carriers. The analysis is limited to the white noise part of the noise spectrum only, and to diodes having large potential drops across the multiplying region of the depletion layer. It is shown for the special case in whichbeta = kalpha , wherek is a constant and α and β are the ionization coefficients of electrons and holes, respectively, that the noise spectral density is given by2eI_{in}M^{3}[1 + (frac{1 - k}{k})(frac{M - 1}{M})^{2}] where M is the current multiplication factor and Iin the injected current, if the only carriers injected into the depletion layer are holes, and by2eI_{in}M^{3}[1 - (1 - k)(frac{M - 1}{M})^{2}] if the only injected carriers are electrons. An expression is also derived for the noise power which will be delivered to an external load for the limitM rightarrow infin . 相似文献
10.
Experimental and analytical investigations have been made on unsaturated gain g0 of a CO2 electric-discharge convection laser, in which discharge current flow, gas flow, and the optical axis are mutually perpendicular. Stable glow discharges in sealed gas mixtures of CO2 , CO, N2 , and He were maintained at pressures up to 780 torr with an input power density of about 90 W/cm3. The ratio of electric field to neutral particle densityE/N was1.7 times 10^{-16} V . cm2and was independent of the total gas pressureP . The electron density in a positive column of the glow discharge was about4 times 10^{10} cm-3. Detailed spatial distributions of g0 at a wavelength near 10.6 μm were measured in the pressure range from 100 to 780 torr. Measurements were also made on the current dependence of g0 and on the change in go with discharge time. The g0 distributions along the gas flow direction were found to agree with those calculated from the electron density distribution and the relaxation rate constant of the upper laser level on the basis of continuity equations for a two-level model. The integrated value of g0 along the flow direction was proportional to P-0.8whenE/N , electron density, and gas temperature were held constant. A maximum value of the g0 distribution, which was proportional to P-0.3, was 0.14 percent/cm at 780 torr. 相似文献
11.
Higher dimensional orthogonal designs and applications 总被引:2,自引:0,他引:2
《IEEE transactions on information theory / Professional Technical Group on Information Theory》1981,27(6):772-779
The concept of orthogonal design is extended to higher dimensions. A properg -dimensional design[d_{ijk cdots upsilon}] is defined as one in which all parallel(g-1) -dimensional layers, in any orientation parallel to a hyper plane, are uncorrelated. This is equivalent to the requirement thatd_{ijk cdots upsilon} in {0, pm x_{1}, cdots , pm x_{t} } , wherex_{1}, cdots , x_{t} are commuting variables, and thatsum_{p} sum_{q} sum_{r} cdots sum_{y} d_{pqr cdots ya} d_{pqr cdots yb} = left( sum_{t} s_{i}x_{i}^{2} right)^{g-1} delta ab, where(s{1}, cdots , s{t}) are integers giving the occurrences ofpm x_{1}, cdots , pm x_{t} in each row and column (this is called the type(s_{1}, cdot ,s_{t})^{g-1}) and(pqr cdots yz) represents all permutations of(ijk cdots upsilon) . This extends an idea of Paul J. Shlichta, whose higher dimensional Hadamard matrices are special cases withx_{1}, cdots , x_{t} in {1,- 1}, (s_{1}, cdots, s_{t})=(g) , and(sum_{t}s_{i}x_{i}^{2})=g . Another special case is higher dimensional weighing matrices of type(k)^{g} , which havex_{1}, cdots , x_{t} in {0,1,- 1}, (s_{1}, cdots, s_{t})=(k) , and(sum_{t}s_{i}x_{i}^{2})=k . Shlichta found properg -dimensional Hadamard matrices of size(2^{t})^{g} . Proper orthogonal designs of type 相似文献
12.
《Electron Device Letters, IEEE》1987,8(4):140-142
Electric-field acceleration factor β is the slope of thelog (t_{BD}) versus Eox curve, where tBD is the time to breakdown at oxide field Eox . We report that β is not a constant but proportional toEmin{ox}max{-2} . This is the main cause of the wide divergence of β values reported in the literature. The reported oxide thickness dependence of β is believed to be a result of the higher electron trap densities in thicker oxides. Oxide lifetime extrapolation usinglog (t_{BD}) , or better,log (Q_{BD}) against1/E_{ox} plots is more accurate and has a theoretical basis. Highly accelerated oxide testing appears to be feasible especially for very thin oxides. 相似文献
13.
Performance analysis and laser linewidth requirements for optical PSK heterodyne communications systems 总被引:1,自引:0,他引:1
An optical PSK heterodyne communications receiver is investigated. The receiver is based on the decision-directed phase-locked loop. The performance of the phase-locked loop subsystem is analyzed taking into account both shot noise and laser phase noise. It is shown that for reliable phase locking (rms phase error less than 10°), heterodyne second-order loops require at least 6771 electrons/s per volt every hertz of the laser linewidth. This number corresponds to the limit when the loop dumping factor η is infinitely large; ifeta = 0.7 , then the loop needs 10 157 electrons/(s . Hz). If the detector has a unity quantum efficiency andlambda = 1.5 mu m, the above quoted numberers give 0.9 pW/ kHz foreta rightarrow infty and 1.35 pW/kHz fornu = 0.7 . The loop bandwidth required is also evaluated and found to be155 Deltanu , whereDeltanu is the laser linewidth. Finally, the linewidth permitted for PSK heterodyne recievers is evaluated and found to be2.26 cdot 10^{-3} R_{b} where Rb is the system bit rate. ForR_{b}=100 Mbit/s, this leads toDeltanu < 226 kHz. Such and better linewidths have been demonstrated with laboratory external cavity lasers. For comparison, ASK and FSK heterodyne receivers are much more tolerant to phase noise,-they can tolerateDeltanu up to 0.09 Rb . At the same time, homodyne receivers impose much more stringent requirements on the laser linewidth (Deltanu < 3 cdot 10^{4} R_{b} ). 相似文献
14.
We have measured gain spectra for TE polarization in a GaInAsP/InP laser as a function of dc bias current below laser threshold. The measurements were made on a low-threshold device with a stripe geometry defined by proton bombardment. A number of other characteristics of this and similar devices from the same wafer are also reported. These data permit the maximum gain coefficient of the active layer gmax to be evaluated as a function of nominal current density Jnom . We obtain the linear relationshipg_{max} = (3.1 times 10^{-2}/eta_{r})(J_{nom} - eta_{r} 5.4 times 10^{3}) , where ηr is the radiative quantum efficiency. Our data apply only for large gain (g gsim 150 cm-1) and large Jnom because the active layer of the test device is thin (0.1 μm). 相似文献
15.
《IEEE transactions on information theory / Professional Technical Group on Information Theory》1981,27(1):132-136
A randomized decision rule is derived and proved to be the saddlepoint solution of the robust detection problem for known signals in independent unknown-mean amplitude-bounded noise. The saddlepoint solutionphi^{0} uses an equaUy likely mixed strategy to chose one ofN Bayesian single-threshold decision rulesphi_{i}^{0}, i = 1,cdots , N having been obtained previously by the author. These decision rules are also all optimal against the maximin (least-favorable) nonrandomized noise probability densityf_{0} , wheref_{0} is a picket fence function withN pickets on its domain. Thee pair(phi^{0}, f_{0}) is shown to satisfy the saddlepoint condition for probability of error, i.e.,P_{e}(phi^{0} , f) leq P_{e}(phi^{0} , f_{0}) leq P_{e}(phi, f_{0}) holds for allf andphi . The decision rulephi^{0} is also shown to be an eqoaliir rule, i.e.,P_{e}(phi^{0}, f ) = P_{e}(phi^{0},f_{0}) , for allf , with4^{-1} leq P_{e}(phi^{0},f_{0})=2^{-1}(1-N^{-1})leq2^{-1} , N geq 2 . Thus nature can force the communicator to use an {em optimal} randomized decision rule that generates a large probability of error and does not improve when less pernicious conditions prevail. 相似文献
16.
《Electron Devices, IEEE Transactions on》1979,26(9):1359-1361
It is shown that the substrate current in GaAs MESFET's may be related to the electron injection into the substrate region adjacent to the high-field domain in the active layer. A simple one-dimensional calculation shows that the substrate current Isub is proportional toVmin{ds}max{1/2} andnmin{0}max{1/4} where Vds is the drain-to-source voltage, n0 is the doping density in the active layer. Atn_{0} = 10^{17} cm-3andV_{ds} simeq 10 V we estimateI_{sub} sim 50 mA per millimeter gate in good agreement with experimental results. 相似文献
17.
《Electron Devices, IEEE Transactions on》1973,20(4):371-379
An analytical investigation supported by numerical calculations has been performed of the stable field profile in a supercritical diffusion-stabilized n-GaAs transferred electron amplifier (TEA) with ohmic contacts. In the numerical analysis, the field profile is determined by solving the steady-state continuity and Poisson equations. The diffusion-induced short-circuit stability is checked by performing time-domain computer simulations under constant voltage conditions. The analytical analysis based on simplifying assumptions gives the following results in good agreement with the numerical results. 1) A minimum doping level required for stability exists, which is inversely proportional to the field-independent diffusion coefficient assumed in the simple analysis. 2) The dc current is bias independent and below the threshold value, and the current drop ratio increases slowly and almost linearly with the doping level. 3) The domain width normalized to the diode lengthL varies almost linearly with(V_{B}/V_{T}-1)^{frac{1}{2}}/(n_{0}L)^{frac{1}{2}} where VB is the bias voltage VT is the threshold voltage, and no is the doping level. 4) The peak domain field varies almost linearly with (V_{B}/V_{T}-1 )^{frac{1}{2}} (n_{0}L)^{frac{1}{2}} . Those results contribute to the understanding of the highn_{0}L -product switch and the stability of the supercritical TEA. 相似文献
18.
《Electron Devices, IEEE Transactions on》1980,27(11):2133-2140
The parameters controlling the photovoltaic properties of the Cu2 S/CdS heterojunction have been investigated. It is found that the behavior of the short-circuit current and the open-circuit voltage are describable in terms of a deep, donor-like level in the CdS region adjacent to the metallurgical interface. When tunneling from this level into the Cu2 S is the mechanism controlling the current flow, theJ_{SC}-V_{OC} characteristics of the device are described by the equationJ_{SC} = J_{00} exp (a_{i}(E_{I} - Phi_{T}_{0})) {exp (a_{i}q V_{OC})-1} where JSC is the short-circuit current, J00 is the current preexponential factor,Phi _{T}_{0} is the zero-bias barrier height in the CdS, EI is the ionization energy of the deep donor, VOC is the open-circuit voltage, and ai is a tunneling factor dependent on the net positive charge density in the CdS near the interface. The relative probability of tunneling from this level to the Cu2 S is derived, as is the probability of tunneling from the level to the CdS conduction band. The photocapacitance effects observed in this junction are attributed to the joint action of this level and an acceptor state due to copper in the CdS. Combining the results from the tunneling calculation, theJ_{SC}-V_{OC} data, and the quenching spectra of the photocapacitance, the ionization energy of the donor level is determined to be 0.45 eV and the density of these levels exceeds 1019cm-3near the interface. The donor level acts as a recombination center, reducing JSC , and as a tunneling center, reducing VOC . Since these levels exist in junctions produced by the dipping method or by the dry method, they set fundamental limits to the efficiency of devices fabricated using these methods. 相似文献
19.
《Electron Devices, IEEE Transactions on》1974,21(1):89-93
Assuming the conventional divisions of the semiconductor into depleted and neutral regions, it is shown that for an abrupt p-n junction with nondegenerate carriers a relation exists between the open circuit photovoltage and the PN product at the junction(PN)_{0} , which is valid for all signal levels. In the small-signal case this leads to the standard result. At intermediate levels a new relationV = KT/q (1 pm m) log_{e} ([(PN)_{0}]^{1/2}/n_{i}) holds, the upper sign for p+-n junctions, the lower for n+-p junctions;m = (micro_{e}-micro_{h})/(micro_{e}+micro_{h}) . At very high levels the photovoltage saturates toV = kT/q[log_{e}(M_{p}M_{n}/n_{i^{2}}) + m log_{e}(micro_{h}M_{p}/micro_{e}M_{N})] . Since Mp and MN are the doping levels in the p and n regions, the first term is the diffusion potential and the second term will be positive for p+-n junctions and negative for n+-p junctions. These results compare satisfactorily with the available experimental data. 相似文献
20.
《Electron Devices, IEEE Transactions on》1971,18(12):1186-1187
The noise temperature as a function of the applied field has been measured on an epitaxial silicon layer at the frequencies 2 GHz and 4 GHz. It has been found that the experimental results are in good agreement with the theory given by Moll. It is shown that for noise calculations in silicon field-effect transistors with pronounced carrier velocity saturation the noise temperature Tn versus field E may be approximated byT_{n}/T_{0} = 1 + γ(E/E_{c})^{2} with T0 = lattice temperature, Ec = saturation field, γ = const. 相似文献