Mechanisms for low-frequency oscillations in GaAs FET's

Miller, Dean J.; Bujatti, M.

doi:10.1109/t-ed.1987.23076

Cited by 29 publications

(5 citation statements)

References 7 publications

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“…A possible cause is that the substrate leakage current recorded in our experiments is only the current from the substrate to the sidegating electrode. In fact, the total leakage current should consist of currents from the FET active region, from the gate pad located on the SI substrate, and from the grounded substrate [5]. In the further research, we will make a thorough investigation on the LFN in leakage current and try to find its relationship with the LFN in drain current.…”

Section: Discussionmentioning

confidence: 99%

“…Miller and Bujatti attributed LFN directly to the oscillations in leakage currents in the semi-insulating (SI) GaAs substrate [5]. While Wager pointed out that LFN in channel current could not be simply attributed to the oscillations in leakage current of the substrate, but related to the peculiarities of channel-substrate junction [9].…”

Section: Citationmentioning

confidence: 99%

“…However, as the demand for higher speeds and increased functionality in circuits, low-frequency noises (LFN) in currents, such as thermal noise, 1/f noise, generation-recombination noise, diffusion noise and shot noise, in various GaAs FET structures have been reported [3][4][5][6][7][8][9][10]. The main characteristics of these noises are: (1) LFN strongly depends upon the substrate materials.…”

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Low-frequency noises in GaAs MESFET’s currents associated with substrate conductivity and channel-substrate junction

Ding

Yan

2011

Chin. Sci. Bull.

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Low-frequency noises in GaAs MESFET are usually observed when investigating the drain current and substrate leakage current under sidegate bias conditions. Experimental results show that the magnitude of low-frequency noises is in a direct dependency upon the sidegate bias and the noises in drain current will disappear if sidegate bias increases more negatively beyond a certain voltage. A mechanism associated with the substrate conductivity and the channel-substrate junction modulated by sidegate bias is proposed to explain the fluctuation of low-frequency noises.MESFET, low-frequency noise, substrate conductivity, channel-substrate junction Citation:Ding Y, Yan X L. Low-frequency noises in GaAs MESFET's currents associated with substrate conductivity and channel-substrate junction. Chinese Sci Bull, 2011Bull, , 56: 1267Bull, −1271Bull, , doi: 10.1007 MESFET is considered as one of the important devices for the applications of high power, high frequency and high efficiency microwave electric circuit [1,2]. However, as the demand for higher speeds and increased functionality in circuits, low-frequency noises (LFN) in currents, such as thermal noise, 1/f noise, generation-recombination noise, diffusion noise and shot noise, in various GaAs FET structures have been reported [3][4][5][6][7][8][9][10]. The main characteristics of these noises are: (1) LFN strongly depends upon the substrate materials. (2) The frequency of LFN is in the range of about 10 −2 to 10 2 Hz. (3) LFN is dependent on the fabrication procedure and bias condition. (4) LFN is sensitive to illumination. Recently LFN has received more attention due to its effect on the performance of low-noise microwave integrated circuits (MMICs).Although it is generally accepted that LFN results from the field-enhanced capture of electrons by deep traps, the exact mechanism is not fully understood. Miller and Bujatti attributed LFN directly to the oscillations in leakage currents in the semi-insulating (SI) GaAs substrate [5]. While Wager pointed out that LFN in channel current could not be simply attributed to the oscillations in leakage current of the substrate, but related to the peculiarities of channel-substrate junction [9].In this paper, LFN in MESFET's currents is investigated under sidegating conditions, and the mechanism is identified whereby the current fluctuation is directly related to the sidegate bias. Unlike Birbas's explanation in terms of an unreal negative capacitance of the depletion region in buffer-channel interface [11], we associate LFN with the substrate conductivity and channel-substrate junction modulated by sidegate bias. This study should be of value to elucidate the fundamental nature of noises modulation in GaAs ICs.

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Section: Discussionmentioning

confidence: 99%

Section: Citationmentioning

confidence: 99%

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confidence: 99%

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Low-frequency noises in GaAs MESFET’s currents associated with substrate conductivity and channel-substrate junction

Ding

Yan

2011

Chin. Sci. Bull.

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“…The LFO phenomena may be understood to occur as a result of field-enhanced capture of electron to EL2 level; that is, the decrease in the free electron concentration due to the field-enhanced capture causes the formation and propagation of a high-electric-field domain. The LFOs cause undesired noises in the actual applications of GaAs FETs [2], and they may be understood as a simple example of nonlinear systems [3]. The sub-linear I-V characteristics, LFO waveforms, and their Fourier-transform spectra (FTS) have been precisely measured by using the three-electrode guard-ring method [4].…”

Section: Introductionmentioning

confidence: 99%

Influence of dislocation on high-electric-field property in semi-insulating GaAs

Kiyama

Yamada

Tatsumi

2004

13th International Conference on Semiconducting and Insulating Materials, 2004. SIMC-XIII-2004.

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High-electric-field properties such as sub-linear I-V characteristic and low-frequency oscillations (LFOs) have been measured in a low-dislocation-density semi-insulating GaAs crystal. It is found that the sub-linear I-V behaviours and LFO waveforms measured at the cathodes where no dislocations exist are very stable but those measured at the cathodes where several dislocations are observed are not stable but more complicated, which is confirmed from Fourier-transform spectra of LFOs. It is explained that the high-electric-field properties observed here depend on the electrical inhomogeneities induced by the dislocations. IntroductionIt is well known that when the DC electric field over 1 kV/cm is applied to a semi-insulating (SI) GaAs crystal, a sub-linear I-V behaviour is observed and then low-frequency oscillations (LFOs) occur [1]. The LFO phenomena may be understood to occur as a result of field-enhanced capture of electron to EL2 level; that is, the decrease in the free electron concentration due to the field-enhanced capture causes the formation and propagation of a high-electric-field domain. The LFOs cause undesired noises in the actual applications of GaAs FETs [2], and they may be understood as a simple example of nonlinear systems [3]. The sub-linear I-V characteristics, LFO waveforms, and their Fourier-transform spectra (FTS) have been precisely measured by using the three-electrode guard-ring method [4]. It should be noticed that the former experiments [4-6] were made in SI-GaAs crystals with high-dislocation density, because low-dislocation density crystals were not easily available. Therefore, there is no work to investigate the relationship between crystal quality and high-electric-field properties. In the present study, we have investigated the influence of dislocations on these properties with a low-dislocation-density GaAs crystal, which is performed by etching of dislocations in the area of cathode electrode after the I-V, LFO, and FTS measurements. We have found the difference in these properties between at the cathodes where no etch-pit exists and at those where several etch-pits exist are observed. Experimental ProcedureThe experimental setup and the three-electrode guard-ring method employed in the present study are shown in Fig. 1. We can measure precisely, stably, and reproducibly I-V, LFO, and FTS characteristics by using this method, because the electric-field distribution is well controlled and uniform in the sample and the surface leakage current is extremely low and reduced in comparison with the two-electrode method [4].We used a low-dislocation-density (001) GaAs wafer grown by the vertical boat method, whose

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“…Although GaAs MESFETS are expected to be used as high-' speed, high-frequency transistors and integrated circuits, some parasitic phenomena, such as the side-gating effect [I], and low-frequency current oscillations (LFOS) [2], are found to be serious problems in practical applications.…”

Section: Introductionmentioning

confidence: 99%

Relationship between the chaotic oscillation and side-gating effect S-type negative differential resistance in GaAs MESFETs

Yano¹,

Goto²,

Ohno³

1992

Semicond. Sci. Technol.

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It is shown that GaAs MESFET drain current low-frequency oscillations (LFOS) correlate with side-gating effect S-type negative differential resistances (SNDRS). The LFOs are observed only around the SNOR region, which appears near an extrapolated cross-point for a low-voltage Ohm's law cuwe and a highvoltage super linear injection current cuwe. The LFO waveforms are chaotic and they vary with temperature and applied side-gate voltage in a complicated way. Fractal dimensions for the LFO waveform are estimated to be 1.7-3.6, which may support the waveform complexity.

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Mechanisms for low-frequency oscillations in GaAs FET's

Cited by 29 publications

References 7 publications

Low-frequency noises in GaAs MESFET’s currents associated with substrate conductivity and channel-substrate junction

Low-frequency noises in GaAs MESFET’s currents associated with substrate conductivity and channel-substrate junction

Influence of dislocation on high-electric-field property in semi-insulating GaAs

Relationship between the chaotic oscillation and side-gating effect S-type negative differential resistance in GaAs MESFETs

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