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تسجيل مستخدم جديدTemperature Dependent Current Dispersion Study in $beta$-Ga$_2$O$_3$ FETs Using Sub-Microsecond Pulsed IV Characteristics
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A comprehensive study of drain current dispersion effects in $beta$-Ga$_2$O$_3$ FETs has been done using DC, pulsed and RF measurements. Both virtual gate effect in the gate-drain access region and interface traps under the gate are most plausible explanations for the experimentally observed pulsed current dispersion and high temperature threshold voltage shift respectively. Unpassivated devices show significant current dispersion between DC and pulsed IV response due to gate lag effect characterized by time constants in the range of 400~$mu s$ to 600~$mu s$. An activation energy of 99~$meV$ is estimated from temperature dependent Arrhenius plots. A variable range hopping based slow transport in conjunction with the observed shallow trap level is attributed to the observed slow transient response of drain current with respect to time. Reactive ion etching step during the device fabrication is most likely responsible for introducing the traps. Effect of traps can be minimized by using surface passivation layers, in this case, Silicon Nitride which shows significant improvement in the current dispersion and RF cutoff frequency. This work demonstrates the detrimental effect the traps can have on the current dispersion which significantly limits the high frequency operation of the device.
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$beta$-Ga$_2$O$_3$ is a promising ultra-wide bandgap semiconductor whose properties can be further enhanced by alloying with Al. Here, using atomic-resolution scanning transmission electron microscopy (STEM), we find the thermodynamically-unstable $g
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Recent breakthroughs in bulk crystal growth of the thermodynamically stable beta phase of gallium oxide ($beta$-Ga$_2$O$_3$) have led to the commercialization of large-area beta-Ga$_2$O$_3$ substrates with subsequent epitaxy on (010) substrates produ
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We introduce a deep-recessed gate architecture in $beta$-Ga$_2$O$_3$ delta-doped field effect transistors for improvement in DC-RF dispersion and breakdown properties. The device design incorporates an unintentionally doped $beta$-Ga$_2$O$_3$ layer a
s the passivation dielectric. To fabricate the device, the deep-recess geometry was developed using BCl$_3$ plasma based etching at ~5 W RIE to ensure minimal plasma damage. Etch damage incurred with plasma etching was mitigated by annealing in vacuum at temperatures above 600 $deg$C. A gate-connected field-plate edge termination was implemented for efficient field management. Negligible surface dispersion with lower knee-walkout at high V$_mathrm{DS}$, and better breakdown characteristics compared to their unpassivated counterparts were achieved. A three terminal off-state breakdown voltage of 315 V, corresponding to an average breakdown field of 2.3 MV/cm was measured. The device breakdown was limited by the field-plate/passivation edge and presents scope for further improvement. This demonstration of epitaxially passivated field effect transistors is a significant step for $beta$-Ga$_2$O$_3$ technology since the structure simultaneously provides control of surface-related dispersion and excellent field management.
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rees well with the experimental data obtain recently, which found that the low-temperature thermal conductivity in this material can reach values above 1000 W/mK. I find that the calculated thermal conductivity of $beta$-Ga$_2$O$_3$ is larger than that of $beta$-In$_2$O$_3$ at all temperatures, which implies that $beta$-Ga$_2$O$_3$ should also exhibit high values of thermal conductivity at low temperatures. The thermal conductivity of KTaO$_3$ calculated ignoring the temperature-dependent phonon softening of low-frequency modes give high-temperature values similar that of $beta$-Ga$_2$O$_3$. However, the calculated thermal conductivity of KTaO$_3$ does not increase as steeply as that of the binary compounds at low temperatures, which results in KTaO$_3$ having the lowest low-temperature thermal conductivity despite having acoustic phonon velocities larger than that of $beta$-Ga$_2$O$_3$ and $beta$-In$_2$O$_3$. I attribute this to the fact that the acoustic phonon velocities at low frequencies in KTaO$_3$ is less uniformly distributed because its acoustic phonon branches are more dispersive compared to the binary oxides, which causes enhanced momentum loss even during the normal phonon-phonon scattering processes. I also calculate thermal diffusivity using the theoretically obtained thermal conductivity and heat capacity and find that all four materials exhibit the expected $T^{-1}$ behavior at high temperatures. Additionally, the calculated ratio of the average phonon scattering time to Planckian time is larger than the lower bound of 1 that has been observed empirically in numerous other materials.
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