2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Fluctuation and Noise Letters Vol. 12, No. 3 (2013) 1350014 (14 pages) c World Scientific Publishing Company DOI: 10.1142/S0219477513500144 ANALYSIS OF NOISE CHARACTERISTICS OF GaAs TUNNEL DIODES Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. VILIUS PALENSKIS∗ , JONAS MATUKAS, JUOZAS VYŠNIAUSKAS and SANDRA PRALGAUSKAITĖ Radiophysics Department, Vilnius University LT-10222 Vilnius, Lithuania ∗vilius.palenskis@ff.vu.lt HADAS SHTRIKMAN Department of Condensed Matter Physics Weizmann Institute of Science Rehovot 76100, Israel DALIUS SELIUTA, IRMANTAS KAŠALYNAS and GINTARAS VALUŠIS Optoelectronics Department Center for Physical Sciences and Technology LT-01108 Vilnius, Lithuania Received 14 December 2012 Accepted 26 June 2013 Published 19 August 2013 Communicated by Francois Danneville An analysis and investigation of noises of GaAs tunnel diodes, which abrupt p+ -n+ profile was obtained by using amphoteric nature of silicon, were performed. The main scope of this work was to verify the concepts of the explanation of white noise characteristics on the ground of shot noise and on the ground of the Gupta theorem of thermal noise in resistive elements. The other scope was to investigate the peculiarities of low frequency noise in p+ -n+ junctions formed by using amphoteric silicon nature. Keywords: Generation-recombination noise; Gupta theorem; shot noise; thermal noise; tunnel GaAs diode noise. 1. Introduction Though the tunnel diode is known many decades ago, at present there is a variety of applications of tunnel diode structures in combination with different semiconductor devices. The tunnel diode contact is used to improve the characteristics of the MOSFET transistors [1], of the laser diodes by integration of multi-quantum-well 1350014-1 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. V. Palenskis et al. tunnel diode [2], of the multi-junction solar cells by incorporation of cascade tunnel diode structure to InAs/GaSb interface to enhance the performance of such cells [3, 4]. The tunnel diodes are used for detection of very small powers (about several picowatts) of millimeter and submillimeter waves [5–7]. They are also used in measurement technique: for surface impedance measurement of superconductors [8], a gated tunnel diode has been introduced into a waveguide oscillator circuit [9, 10] to tune the oscillation frequency and to turn the oscillator on and off [10]. A very attractive is investigation of electronic transport in GaSb/InAs(Sb) nanowire tunnel diodes [11] for developing tunnel-field-effect transistors. The relation between charge carrier scattering and fluctuations at equilibrium conditions was determined over a decade ago: the fluctuations cause the scattering mechanism of energy, and the dissipative systems are influenced by the thermal fluctuations. The relation between the diffusion coefficient and mobility of randomly moving charge carriers and the Nyquist theorem for thermal noise confirm this relation [12, 13]. The relation with nonlinearity of resistive systems was defined by Gupta only 50 years later than the Nyquist theorem [14, 15]. Gupta related the thermal noise spectral density with phenomenological characteristics of nonlinear resistive system. At low frequencies the tunnel diode also as p-n junction and Schottky diodes can be presented as nonlinear resistor with particular current–voltage characteristic. In many cases it is stated that the tunneling component of current produces the shot noise, which is described by Schottky formula [16–19]. In [20] and [21], it has been shown, that the p-n junction diodes and the Schottky-barrier diodes in the range of the white spectrum is consistent with the idea of thermal noise in nonlinear resistive elements independently of technology and non-ideality of current–voltage characteristics, and is well described by Gupta formula. The Schottky formula is applicable only for ideal exponential current–voltage characteristics, caused due to diffusion process. Considering that these two ways for explanation of the white noise sources are different, it is very interesting to verify, which one is more near to experimental results for tunnel diodes. In this paper we present a detail investigation of noise characteristics of GaAs tunnel diodes. The other scope was to investigate the low-frequency noise characteristics of GaAs tunnel diodes, which p+ -n+ junction abrupt doping profile was achieved by using amphoteric nature of silicon on GaAs surface. 2. Samples and the Measurement Technique The investigated p+ -n+ structures were grown by molecular beam epitaxy on semiinsulating GaAs substrates. High carrier densities as well as abrupt doping profile were achieved by using amphoteric nature of silicon on (311)A GaAs substrate [22]. Technologically, at high growth temperatures (>660◦C) and low As/Ga flux ratio (≈ 1), Si atoms predominantly incorporate on As sublattice sites and behave as uncompensated acceptors, while at low growth temperature (<500◦ C) and at high As/Ga flux ratio (>2.5) Si atoms occupy Ga sublattice sites and act as donors. 1350014-2 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. Analysis of Noise Characteristics of GaAs Tunnel Diodes Fig. 1. A view of the quadratic mesa structure of the GaAs tunnel diode. The upper Ni-Au-Ge alloy electrode layer area is (100 µm × 100 µm), n+ = 3 · 1018 cm−3 layer thickness is 0.4 µm, and the area is (120 µm × 120 µm); p+ = 5 · 1019 cm−3 layer thickness is 0.6 µm. Round the mesa structure there is the ohmic contact: the side stripline of the square is equal 1.2 mm, and the stripline width is 0.15 mm. PC ADC LNA A + ¯ RL1 E Ret C V TD Fig. 2. The measurement circuit: TD is the GaAs tunnel diode; RL1 is the load resistance, which assures the constant direct current regime; LNA is the very low noise amplifier; PC is the personal computer; ADC is the analog-to-digital converter (National InstrumentTM PCI 6115 board); E is the storage battery; Ret is the standard resistor; C is the capacitor for shunting the noise from supply system. The samples were with alloyed Ni-Au-Ge contacts. A view of measured samples is shown in Fig. 1. The tunnel diode noise measurement circuit is presented in Fig. 2. The tunnel diode noise properties were investigated at low forward voltages up to peak current and at backward voltages in order to verify the Gupta theorem. For noise measurement there was designed very low noise amplifier. The comparison of the noise levels between own measurement system to that of tunnel diode at zero bias is presented 1350014-3 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 V. Palenskis et al. V d=0 -18 2 S u, V s 10 syst. 10 -19 10 3 10 4 10 5 10 6 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. f, Hz Fig. 3. Comparison of the noise levels between the own measurement system to that of tunnel diode at Vd = 0. in Fig. 3. It is seen that the white noise level of the measurement system is about an order smaller than that of tunnel diode at zero bias voltage. The spectral density of tunnel diode noise was evaluated by comparison with thermal noise of standard resistor Ret : SV = 2 −V2 Vtd syst 2 Vet2 − Vsyst · 4kT 0 Ret , (1) 2,V 2 2 where Vtd syst and Vet respectively are the tunnel diode, the measuring system, and the standard resistor thermal noise variances in the narrow frequency band ∆f ; T0 is the absolute temperature of the standard resistor. 3. Experimental Results and Their Analysis 3.1. Investigation of white noise characteristics of GaAs tunnel diode As was mentioned in introduction, in literature there are two concepts (on the ground of shot noise, and on thermal noise of nonlinear resistive elements) for explanation of the white noise sources in different p-n junctions, it was very interesting to verify, which one is more near to experimental results for GaAs tunnel diodes. A schematic energy diagram of the tunnel diode is shown in Fig. 4. The position of the Fermi energy for electrons ∆EFn and for holes ∆EFp of high degenerated materials can be evaluated from these expressions [23, 24]: ∆EFn = (2 /2m∗dn ) · (3π 2 n)2/3 and ∆EFp = (2 /2m∗dp ) · (3π 2 p)2/3 , (2) where n is the density of free electrons in conduction band; p is the free holes density in valence band; = h/2π is the Plank’s constant; the effective mass of density of states for electrons in GaAs mdn ≈ 0.064m0 [25] and the position of the 1350014-4 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Analysis of Noise Characteristics of GaAs Tunnel Diodes p + n Ec Eg Ev E Fp + "Tails" of density of states eVp eVn EFn Ec Fig. 4. Schematic energy diagram of the tunnel diode. The potentials Vn and Vp reflect the degrees of the degeneracy of n+ -region and p+ -region, respectively. 6 Imax Exp. 4 Calc. 2 I, mA Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. Ev 0 Vp -2 Vpexp -4 -6 -600 -300 0 300 600 900 1200 V d, mV Fig. 5. Current–voltage characteristic of GaAs tunnel diode. Exp. is the direct measurement curve, and Calc. is the calculated curve by eliminating the voltage Ir ser due to serial resistance rser of the tunnel diode. Fermi energy ∆EFn ≈ 0.12 eV, and the effective mass of density of states for holes mdh ≈ 0.61m0 [25] and ∆EFp ≈ 0.08 eV; here m0 is the free electron mass. The typical current–voltage characteristic of the investigated GaAs tunnel diodes is presented in Fig. 5. The current peak of the directly measured results shows that it happens at higher bias voltage Vpexp than it follows from the tunnel diode diagram: the current peak has to occur at bias voltage when the Fermi energy ∆EFn coincides with the top of the valence band [26], i.e., when Vd = Vp ≈ 0.08 V. For investigated tunnel diodes the voltage difference (Vpexp − Vp ) is due to serial resistance rser = (Vpexp − Vp )/Imax of the tunnel diode structure. In Fig. 5, it is also shown the calculated current–voltage characteristic (curve Calc.) by eliminating the voltage Ir ser due to serial resistance. The spectral density of voltage fluctuations 1350014-5 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 10 -11 10 -13 10 -15 10 -17 V d, V: 0.53 0.60 0.80 1.00 1.15 1/f 2 S v, V s V. Palenskis et al. Vd, mV: 0 66 10 1 105 183 10 2 300 10 3 341 10 4 Fig. 6. Spectral density of voltage fluctuations dependence on frequency (in the frequency range from 10 Hz to 20 kHz) at different forward voltages of tunnel diode. dependence on frequency at different forward biases in the frequency band from 10 Hz to 20 kHz is presented in Fig. 6. It is seen that in this frequency band at biases lower than that for current peak prevails the generation-recombination noise, but at higher voltages (>0.53 V, i.e., when energy Ec in n+ region is larger than Ev in p+ region) there is 1/f -type noise due to localized centers of defects in the forbidden energy gap near the interfaces of p+ -n+ junction [26], which cause the leakage current due to charge carrier tunneling to these centers and subsequent their recombination. As it can be seen from Fig. 6, in order to measure the white noise level, it is needed to measure the noise at higher frequencies. For this purpose, the very low noise amplifier was designed that led to the investigation of the tunnel diode noise characteristics of up to 2 MHz (Fig. 3). The noise spectra of GaAs tunnel diode at different forward and backward biases at room temperature are shown in Fig. 7. 10 -16 10 -17 10 -18 10 -19 10 101.5 V d, mV: 125.1 151.9 200.2 250.2 306.4 341.7 381.6 407.3 0 25.1 75.1 50.3 10 3 10 -17 V d , mV: -152.2 -201.4 -250.8 -303.8 -350.4 -404.5 2 -15 S V, V s 10 2 S V, V s Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. f, Hz 10 -18 0 -25.2 -50.6 -102.3 syst. syst. 4 10 5 10 6 f, Hz 10 -19 10 3 10 4 10 5 10 6 f, Hz Fig. 7. Noise spectra of GaAs tunnel diode at different forward (on the left) and backward (on the right) biases at room temperature T = 293 K. 1350014-6 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Analysis of Noise Characteristics of GaAs Tunnel Diodes The differential resistance of Exp. curve (Fig. 5) Rd = dV/dI = rser + rd , where rd is differential resistance of Calc. curve (Fig. 5). These differential resistances are presented in Fig. 8. The spectral density of voltage thermal noise calculated from Eq. (3) is presented in Fig. 9 by dashed line. The measurement results are also shown in this figure by black dots. These investigations directly show that though the Gupta theorem gives good coincidence for white noise level in the case of exponential current– voltage characteristics for p-n junctions [20, 21], but for investigated GaAs tunnel diodes here coincidence is only at backward currents where the current–voltage characteristic is caused by the serial resistance. In the case of forward currents the white noise level cannot be explained on the ground of thermal noise of nonlinear resistive elements. From the equivalent circuit (Fig. 10) follows that spectral density of voltage fluctuations of real GaAs tunnel diode for white noise can be expressed as SV = 4kTR d + 2qIr 2d = 4kT (rser + rd ) + 2qIr 2d . (4) This expression of spectral density is presented in Fig. 9 by solid line. Thus, the spectral density of white noise of investigated GaAs tunnel diodes consists 100 Rd R d, r d , Ω Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. The white noise exceeds the generation-recombination noise level at frequencies higher than 100 kHz. It is interesting to note that white noise level at backward currents almost does not depend on the current magnitude. It is very strange from the view of tunneling, because one believes that there will be shot noise, which has to increase with current increase. According to the Gupta theorem [14, 15], the spectral density SV of voltage thermal fluctuations of nonlinear resistive elements can be presented as 1 d2 V dV + I 2 . (3) SV = 4kT dI 2 dI I=const rd 10 -6 -4 -2 0 2 4 6 I, mA Fig. 8. The differential resistances of investigated GaAs tunnel diodes. Rd = rser + rd ; rser is the serial resistance, and rd is differential resistance due to charge carriers tunneling through the p+ -n+ potential barrier. 1350014-7 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 V. Palenskis et al. 10 -17 2 S V, V s Thermal+ shot noises Gupta 10 -18 -6 -4 -2 0 2 4 6 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. I, mA Fig. 9. The white noise level dependence on the forward and backward currents of the GaAs tunnel diode. Black dots are the measurement results; dashed line is calculated by Eq. (3); solid line is calculated by Eq. (4). of two components: thermal noise due to differential resistance of the tunnel diode, and shot noise caused by the tunneling of the charge carriers through the p+ -n+ junction. These investigations show that white noise of tunnel diodes cannot be explained on the ground of Gupta theory [14, 15] for nonlinear resistive elements. Thus, the experimental result that shot noise often is not observed at backward currents and sometimes at forward currents can be explained in such a way: a real tunnel junction differential resistance rd is many times smaller than the total differential resistance of the tunnel diode, and the shot noise is shunted by rd (Fig. 10). 3.2. Investigation of generation-recombination noise characteristics of GaAs tunnel diodes The other scope was to investigate the low-frequency noise characteristics of GaAs tunnel diodes, which p+ -n+ junction abrupt doping profile was achieved by using amphoteric nature of silicon on GaAs. A detail pattern of the generationrecombination noise spectra of investigated tunnel diodes at forward currents is shown in Fig. 11. They have the Lorentzian type spectrum. The fact that at higher frequencies generation-recombination noise decreases as 1/f shows, that there is rd rser e(t) i(t) Fig. 10. The equivalent white noise circuit of the investigated GaAs tunnel diodes. The voltage noise source e(t) is caused by the thermal noises of resistances rser and rd ; the current noise source i(t) is due to charge carriers tunneling through the p+ -n+ potential barrier. 1350014-8 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Analysis of Noise Characteristics of GaAs Tunnel Diodes 10 -15 10 -16 V d, mV: 391 ~1/f 300 2 S V gr, V s 349 252 10 -17 10 -18 200 153 101 51 10 0 1 10 2 10 3 10 4 Fig. 11. Generation-recombination noise spectra at different forward bias voltages at room temperature T = 293 K. 10 -12 10 -13 10 -14 10 -15 10 -16 10 -17 2 SV gr *f , V Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. f, Hz V d, mV: 391 349 300 252 200 153 101 51 10 1 10 2 10 3 10 4 f, Hz Fig. 12. Normalized generation-recombination noise spectra SV voltages at room temperature T = 293 K. gr · f at different forward bias a distribution of relaxation times. In order to evaluate the distribution of these relaxation times it is convenient to present the normalized spectral density SV gr · f of this noise (Fig. 12). The flat part of the normalized spectral density SV gr · f over the frequency 1 kHz shows that relaxation times for generation-recombination noise at room temperature are distributed in wide time range: approximately from 0.2 ms to about 7 µs. It is interesting to note that this distribution of relaxation times does not depend on the forward current up to the peak current. The spectral density of voltage fluctuations in the above mentioned frequency band at backward biases also has relaxation behavior (Fig. 13). Usually the level of generation-recombination noise in materials is proportional to the square of current (or voltage) [27]. The intensity of generation-recombination noise at backward biases is approximately proportional to the square of current as in the case 1350014-9 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 V. Palenskis et al. 10 -16 2 S V gr , V s V d, mV: -300 10 -17 -185 -106 -66,5 10 0 -18 10 1 10 2 10 3 10 4 Fig. 13. Generation-recombination noise spectra at different backward bias voltages at room temperature T = 293 K. 10-13 Exp. (SV gr/Vrd2 )0*(rd/rd 0) Sv gr/Vrd2 , s Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. f, Hz (SV gr/Vrd2)0 10-14 0 20 40 60 80 100 Vrd, mV 2 dependence on Fig. 14. The intensity of normalized generation-recombination noise SV gr0 /Vrd forward bias voltage Vrd = Vd − Ir ser of p+ -n+ junction (black dots). The open circles represent 2 ) ∗ (r /r ), where r the quantity (SV gr0 /Vrd 0 d d0 d0 is equal rd at Vrd = 0. of material, but at forward currents the noise intensity increases more steeply. It shows that generation-recombination noise is related with p+ -n+ junction. Normalized with respect to voltage Vrd generation-recombination noise spectral density 2 dependence on forward voltage Vrd = Vd − Ir ser is presented in Fig. 14 SV /Vrd by black dots. When the forward voltage increases, the differential resistance rd of the p+ -n+ junction increases, i.e., the effective number of free carriers Neff in the p+ -n+ junction range decreases with increasing of the differential resistance 2 has to increase as a rd . So, if this effect take place, the spectral density SV /Vrd relative differential resistance rd /rd0 , where rd0 is the differential resistance rd at 2 )0 ∗(rd /rd0 ) is presented in Fig. 14 Vrd = 0. The normalized spectral density (SV /Vrd by open circles. It is seen that there is a sufficiently good agreement between the 2 2 and the calculated (SV /Vrd )0 ∗ (rd /rd0 ) quantities. experimental values of SV /Vrd 1350014-10 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 10 -15 10 -16 10 -17 10 -18 10 -19 T, K: 249.7 262.7 275.5 288.0 2 S V, V s Analysis of Noise Characteristics of GaAs Tunnel Diodes 300.9 313.6 327.6 10 1 10 2 339.8 10 3 10 4 Fig. 15. Generation-recombination noise spectra of GaAs tunnel diode at different temperatures and at constant current 3.3 mA. 262.7 288.0 275.5 249.7 10 -14 10 -15 2 S Vf , V Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. f, Hz 10 238.6 300.9 313.6 327.6 339.8 -16 10 1 10 2 10 T , K: 3 10 4 f, Hz Fig. 16. Normalized generation-recombination noise spectra SV gr f at different temperatures (white noise level was eliminated), and at constant current 3.3 mA. The typical generation-recombination noise spectra of investigated GaAs tunnel diodes at different temperatures are shown in Fig. 15. The maximum of the normalized spectral density SV gr · f function (Fig. 16) is at ω0 τ = 1. The flat maximum shows that relaxation times are distributed in wide time range: τ1 /τ2 ≈ 30. The relaxation times of generation-recombination noise and its distribution dependence on temperature are presented in Fig. 17. The temperature dependence of relaxation times can be presented as τ = τ0 exp( ∆E kT ) with the activation energy ∆E ≈ Eg min /2 ≈ 0.53 eV. The energy gap Eg narrows in the p+ -n+ interface to Eg min due to high doping of GaAs, and due to formation of “tails” of density of states below the bottom of conduction band and above the top of valence band (Fig. 4) [24, 25]. The every “tail” of density of states occupies about (0.1–0.15) eV energy range. It is expected that activation energy ∆E and its independence on forward current up to peak value 1350014-11 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 τ , ms V. Palenskis et al. 10 1 10 0 ∆ E =0.53 eV 10 -1 10 -2 10 -3 τ 2.8 3.0 3.2 3.4 3.6 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. 1000/T , K 3.8 4.0 -1 Fig. 17. The relaxation time of generation-recombination noise dependence on temperature at constant current 3.3 mA. and intensive charge carrier recombination noise is related due to recombination process in states of the “tails” in p+ -n+ interface. 4. Conclusion It is shown that GaAs tunnel diodes, grown by molecular beam epitaxy on semiinsulating GaAs substrates with abrupt p+ -n+ profile by using amphoteric nature of silicon have at low frequencies intensive relaxation type noise. The distribution of the relaxation times and their dependence on temperature show that this noise is related with the charge carrier tunneling and recombination processes in states of “tails”. There is presented the equivalent circuit of white noise sources. The performed investigations show that white noise of tunnel diodes cannot be explained on the ground of Gupta theory for nonlinear resistive elements. The spectral density of white noise of investigated GaAs tunnel diodes consists of two components: thermal noise caused by the total differential resistance of the tunnel diode, and shot noise due to the tunneling of the charge carriers through the p+ -n+ junction. The shot noise is shunted by differential resistance of the tunneling junction. Acknowledgments The study was funded in part from the European Community’s social foundation under Grant Agreement No. VP1-3.1-ŠMM-08-K-01-004/KS-120000-1756. References [1] J. Luo, J. Chen, Q. Wu, Zh. Chai, J. Zhou, T. Yu, Y. Dong, L. Li, W. Liu, Ch. Qiu and X. Wand, A tunnel diode body contact structure for high-performance SOI MOSFETs, IEEE Trans. Electron. Dev. 50 (2012) 101–107. [2] B. Niu, Y. Li, T. Hong, W. Chen, S. Liang, J. Pan, J. Qiu and Ch. Wang, DC characterizations of MQW tunnel diode and laser diode hybrid integration device, IEEE Photon. Technol. Lett. 24 (2012) 1369–1371. 1350014-12 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. Analysis of Noise Characteristics of GaAs Tunnel Diodes [3] S. H. Lim, Ch. R. Allen, D. Ding, X. Liu, J. K. Furdyna, D. Vasilevska and Y.H. Zhang, Cascade tunnel diode incorporating In/GaSb broken gap interface for multi-junction solar cells, 37th IEEE Photovoltaic Specialists Conf., 2011, (2011), pp. 000252–000255. [4] G.-H. Hong and P. 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Phys. 72 (1992) 3129–3135. 1350014-13 2nd Reading August 14, 2013 16:38 WSPC/S0219-4775 167-FNL 1350014 V. Palenskis et al. Fluct. Noise Lett. 2013.12. Downloaded from www.worldscientific.com by Dr. Sandra Pralgauskait on 10/01/13. For personal use only. [23] N. W. Ahcroft and N. D. Mermin, Solid State Physics (Holt Rinehart & Winston, 2002). [24] K. V. Shalimova, Physics of Semiconductors (LAN, Moscow, 2010). [25] A. Dargys and J. Kundrotas, Handbook on Physical Properties of Ge, Si, GaAs and InP (Science and Encyclopedia Publishers, Vilnius, 1994). [26] S. M. Sze, Physics of Semiconductor Devices, 2nd edn. (John Wiley & Sons, New York, 1981). [27] A. van der Ziel, Noise in Solid State Devices and Circuits (Wiley-Blackwell, 1986). 1350014-14