Determination of deep trap concentration at channel–substrate interface in GaAs MESFET using sidegating measurements

Khuchua, Nina; Khvedelidze, Levan; Gorev, Nikolai B.; Privalov, E.N.; Shur, M. S.

doi:10.1016/s0038-1101(02)00060-6

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…The observed hysteresis can be interpreted as a result of the junction between substrate and channel related to EL 2 traps whose roles have been recognized in the studies of the sidegating effect [6][7][8][9]. The space-charge distribution of the C-S junction resembles a p-n junction with depletion region located in doped channel and formed by the charge of ionized donors.…”

Section: Resultsmentioning

confidence: 91%

Effects of channel-substrate interface on hysteresis of sidegating effect in GaAs MESFETs

Ding

Yan

2010

Chin. Sci. Bull.

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With sidegating bias, hysteresis of sidegating effect is usually observed in drain current. The experimental results presented in this letter demonstrate that the hysteresis with time-based characteristics is closely related to EL 2 traps and channel-substrate (C-S) junction peculiarities. The response of depletion region of C-S junction to the electron capture and emission by trap-EL 2 plays an important role in the hysteresis. Furthermore, a new mechanism is proposed to explain the time-based characteristics of hysteresis, i.e., there is a "steady-state" in which the hysteresis disappears. GaAs MESFET, sidegating bias, hysteresis, channel-substrate interface Citation:Ding Y,Yan X L. Effects of channel-substrate interface on hysteresis of sidegating effect in GaAs MESFETs.MESFET is considered as one of the important devices for the applications of high power, high frequency and high efficiency RF&MW electric circuit [1]. However, the demand for higher speeds and increased functionality in circuits using GaAs MESFETs has led to a continual reduction in dimensions and an increase in circuit density. Higher density has led to increased sensitivity to sidegating effect, and requires careful layout design rules. In particular, these devices can exhibit an abrupt decrease in drain current at high voltage across the electrode which is set near the MESFET, known as sidegating effect [2]. In this paper, the hysteresis of sidegating effect is investigated, and it is proposed that this is due to the channel-substrate interface. Hysteresis is usually observed in drain current (I DS ) as a function of negative sidegate bias voltage (V SG ) when measuring the threshold behavior of sidegating effect [2,3] in GaAs MESFETs on the voltage-controlled condition [4,5]. When V SG varies positively or negatively, I DS follows different paths and shows apparent hysteresis. This phenomenon has been attributed to the S-type negative differential conductivity of the substrate [4] and the Schottky *Corresponding author (email: dingy@vlsi.zju.edu.cn) contact to the substrate [5]. However, experimental results presented in this letter demonstrate that the response of channel-substrate junction's depletion region to the electron capture and emission by trap-EL 2 plays an important role in the hysteresis. Furthermore, a so-called "steady-state" exists where the hysteresis disappears. This phenomenon disagrees with previous reports.

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Section: Resultsmentioning

confidence: 91%

Effects of channel-substrate interface on hysteresis of sidegating effect in GaAs MESFETs

Ding

Yan

2010

Chin. Sci. Bull.

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“…Sidegating effect is that I DS of MESFET will decrease abruptly when sidegate bias increases beyond a critical value [12,13]. And this critical value is defined as sidegating threshold voltage (V th SG ).…”

Section: Experiments and Resultsmentioning

confidence: 99%

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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Non-destructive deep trap diagnostics of epitaxial structures

Gorev¹,

Kodzhespirova²,

Privalov³

et al. 2003

Solid-State Electronics

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Determination of deep trap concentration at channel–substrate interface in GaAs MESFET using sidegating measurements

Cited by 6 publications

References 8 publications

Effects of channel-substrate interface on hysteresis of sidegating effect in GaAs MESFETs

Effects of channel-substrate interface on hysteresis of sidegating effect in GaAs MESFETs

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

Non-destructive deep trap diagnostics of epitaxial structures

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