Highly doped thin-channel GaN-metal–semiconductor field-effect transistors

Gaška, R.; Shur, M. S.; Hu, X.; Yang, J.; Tarakji, A.; Simin, Grigory; Khan, Asif; Deng, Jie; Werner, Thomas R.; Rumyantsev, Sergey; Pala, Nezih

doi:10.1063/1.1344577

Cited by 29 publications

(10 citation statements)

References 10 publications

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“…Since it is widely known that drain current collapse takes place in a pronounced way in SiO 2 -passivated devices, a SiO 2 film formed by the standard plasma chemical vapor deposition process using SiH 4 and N 2 O on the HF treated AlGaN surface was chosen as the test passivation structure to clarify the collapse mechanism. It has been also reported that Si 3 N 4 -passivation significantly reduces the current collapse.…”

Section: Methodsmentioning

confidence: 99%

“…Being stimulated by recent explosive success of nitride based lasers and light emitting diodes in blue and ultraviolet regions, electronic devices such as AlGaN/GaN heterostructure field effect transistors ͑HFETs͒, 1-3 high-power metalsemiconductor field effect transistors ͑MESFETs͒, 4 and power rectifiers 5 have also made remarkable progress in recent years, resulting in unprecedented high power performances in microwaves and millimeter wave regions. Many workers believe that the AlGaN/GaN HFET will become the key device in the next-generation high frequency power electronics.…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of current collapse and gate leakage currents in AlGaN/GaN heterostructure field effect transistors

Hasegawa

Inagaki

Ootomo

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

213

148

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In order to clarify the mechanisms of drain current collapse and gate leakage currents in the AlGaN/GaN heterostructure field effect transistor ͑HFET͒, detailed electrical properties of the ungated portion and Schottky-gated portion of the device were investigated separately, using a gateless HFET structure and an AlGaN Schottky diode structure. The gateless device was subjected to plasma treatments and surface passivation processes including our novel Al 2 O 3 -based surface passivation. dc I -V curves of gateless HFETs were highly nonlinear due to virtual gating by surface states. After drain stress, air-exposed, H 2 plasma-treated and SiO 2 -deposited gateless HFETs showed an initial large-amplitude exponential current transient followed by a subsequent smaller, slow, and highly nonexponential response. The former was explained by emission from deep donors at E c Ϫ0.37 eV, and the latter by emission from surface states. Capture transients with stress-dependent capture barriers were also observed. An x-ray photoelectron spectroscopy ͑XPS͒ study indicated that 0.37 eV-deep donors are N-vacancy related. On the other hand, no current transients took place in N 2 plasma treated and Al 2 O 3 -passivated samples. Temperature dependences of I -V curves of Schottky diodes were extremely small and reverse currents were anomalously large. They were explained by the ''thin surface barrier'' ͑TSB͒ model where thermionic field emission and field emission through the TSB region formed by deep donors produce leakage current paths. By combining the results on gateless HFETs and Schottky diodes, a new unified model of near-surface electronic states for the free surface and Schottky interface of AlGaN is proposed. It consists of a U-shaped surface state continuum and N-vacancy related near-surface discrete deep donors. The model can explain the observed large gate leakage and drain current collapse in AlGaN/GaN HFETs in a unified way. It is also shown that our novel Al 2 O 3 passivation, when also used as a gate insulator, can completely suppress current collapse and gate leakage.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanisms of current collapse and gate leakage currents in AlGaN/GaN heterostructure field effect transistors

Hasegawa

Inagaki

Ootomo

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

213

148

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“…Among these, GaN has received much attention because of the superior electronic properties such as direct wide band gap, larger electron saturation velocity, lower ohmic contact resistances, and longer minority carrier lifetimes [1,2]. Lately, GaN-based devices have been demonstrated to achieve high performance standards at microwave frequencies and elevated temperatures [3][4][5][6][7][8][9][10][11], which are comparable to that obtained by conventional and mature Si-and GaAs-based devices. GaN-based reliable and efficient linear rf amplifiers and oscillators have found use in life-cycle cost advanced multifunctional rf systems (AMRFS) for military applications while the ultra-high power switches and diodes are being envisaged for use in the power utility industry to eliminate power sags and switching transients [2].…”

Section: Introductionmentioning

confidence: 98%

Parasitic element dependent scattering parameter evaluation of GaN MESFET

Singh¹,

Bose²,

Gupta³

et al. 2002

Micro & Optical Tech Letters

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that its resonant frequency is far beyond the operating bandwidth of the antenna, thus minimizing the back radiation. The two orthogonal polarizations (Figures 1 and 2) including microstriplines are made in two different layers. This feeding technique is preferable, as it improves decoupling between the ports. The parameters of the antenna were optimized with the use of the electromagnetic software package Ansoft Ensemble. The two corporate feed networks were optimized with the use of LINMIC as well as Ansoft Ensemble. EXPERIMENTAL RESULTS AND DISCUSSIONIn order to characterize the planar array antenna for input impedance and mutual coupling as a function of frequency, the return loss and coupling coefficient were measured at both feeding ports. The bandwidth was around 20% at both ports for horizontal and vertical polarizations over the frequency range; the coupling coefficient varied from below Ϫ20 to Ϫ23 dB. The measured S parameters are shown in Figure 3.The measured array radiation patterns are shown in Figures 4 and 5 in both the elevation and azimuth planes at a horizontal port. The radiation pattern for the port exhibits almost similar characteristics. The patterns at the band edges as well as at the center frequency are given in the same figures. Measurements were carried out for both co-and cross polarization. The radiation patterns show at both ports a first side-lobe level between Ϫ14 and Ϫ18 dB for both planes. The cross-polarization performance over the band was found to be within Ϫ19 and Ϫ22 dB. The beamwidths at the azimuth and elevation planes are, respectively, 11°a nd 36°at the center frequency. The measured gain is approximately 17 dBi. As compared to the performance of the single radiating element, which exhibits 26% bandwidth, the array bandwidth is reduced to 20%. This is attributed to the mutual coupling between the antenna elements and the coupling due to microstrip lines in the feed network disturb the power weightings (and therefore the side-lobe levels). All these factors also contribute to an increase in the cross-polarization level. Figure 6 shows a photo of the fabricated array. CONCLUSIONBroadband performance of a 3 ϫ 6-element array antenna has been achieved with the use of a stacked SSFIP antenna with stacked feed lines for dual polarization. The measured results show desired bandwidth performance as well as very low back radiation on the order of Ϫ30 dB, thus ensuring better gain. The isolation between the ports is better than Ϫ23 dB, and cross-polarization suppression is between Ϫ19 and Ϫ22 dB. ACKNOWLEDGMENTThe authors thank Director SAC for necessary support and encouragement.

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“…Excellent candidates for such high power and high frequency operation are the GaNbased devices due to the wide bandgap, high saturation velocity, and high breakdown electric field. GaN metal-semiconductor field-effect transistors (MESFETs) [1,2] and GaN/AlGaN high electron mobility transistors (HEMTs) [3] have been investigated and their advantages over the conventional GaAs technologies have been shown. Motivated by the recent progress of the GaN-based fabrication technology, simulation techniques are being rapidly developed.…”

Section: Introductionmentioning

confidence: 99%

Frequency analysis of GaN MESFETs using full‐band cellular Monte Carlo

Yamakawa

Goodnick

Branlard

et al. 2005

phys. stat. sol. (c)

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A full-band electron transport calculation in wurtzite phase GaN based on a detailed model of the electron-phonon interactions using a Cellular Monte Carlo (CMC) approach is applied to the frequency analysis of MESFETs. Realistic polar-optical phonon, impurity, piezoelectric and dislocation scattering is included in the full-band CMC simulator, which shows good agreement with measured velocity-field data. The effect of the dislocation scattering on the MESFET RF characteristics is examined as well, indicating that the computed cut-off frequency is affected by the crystal dislocation density and bias conditions.

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Highly doped thin-channel GaN-metal–semiconductor field-effect transistors

Cited by 29 publications

References 10 publications

Mechanisms of current collapse and gate leakage currents in AlGaN/GaN heterostructure field effect transistors

Mechanisms of current collapse and gate leakage currents in AlGaN/GaN heterostructure field effect transistors

Parasitic element dependent scattering parameter evaluation of GaN MESFET

Frequency analysis of GaN MESFETs using full‐band cellular Monte Carlo

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