Abstract
In order to study the effect of self-heating of AlGaN/ GaN high electron mobility transistors (HEMTs) characteristics fabricated on Si(111) substrate, simulations of 2DEG temperature on different drain voltages have been carried out by Sentaurus TCAD simulator tool. Prior to the electrical direct-current (DC) characteristics studies, structural properties of the HEMT structures were examined by scanning transmission electron microscopy. The comparative analysis of simulation and experimental data provided sheet carrier concentration, mobility, surface traps, electron density at 2DEG by considering factors such as high field saturation, tunneling and recombination models. Mobility, surface trap concentration and contact resistance were obtained by TCAD simulation and found out to be ∼1270cm2/Vs, ∼2×1013 cm-2 and ∼0.2 Ω.mm, respectively, which are in agreement with the experimental results. Consequently, simulated current-voltage characteristics of HEMTs are in good agreement with experimental results. The present simulator tool can be used to design new device structures for III-nitride technology.
Highlights
The GaN based materials system has proved its capability for high power, high frequency and high temperature devices due to its wide band gap, high saturation velocity and high breakdown voltage.[1,2,3,4] Epitaxial AlGaN/GaN heterostructure forms two-dimensional electron gas (2DEG) at the interface due to the unique polarization properties of III-Nitride materials.[5,6] The spontaneous polarization and piezoelectric polarizations play an important role in the formation of 2DEG at the AlGaN/GaN interfaces
We provide a comparison of a simulated device with the experimental results along with the effect of self-heating on the AlGaN/GaN high electron mobility transistors (HEMTs) device on Si substrate
In the device shown in figure 1, since there is an uninterrupted growth of GaN layer without any interlayer[14] we considered the heat flow from HEMT active layers to the Si substrate, in order to calculate thermal resistance
Summary
The GaN based materials system has proved its capability for high power, high frequency and high temperature devices due to its wide band gap, high saturation velocity and high breakdown voltage.[1,2,3,4] Epitaxial AlGaN/GaN heterostructure forms two-dimensional electron gas (2DEG) at the interface due to the unique polarization properties of III-Nitride materials.[5,6] The spontaneous polarization and piezoelectric polarizations play an important role in the formation of 2DEG at the AlGaN/GaN interfaces. Physical models that defined in sentaurus TCAD are used for analyzing bandgap, carrier mobility, gate tunneling, charge transport, piezoelectric polarization for device characteristics. Chang et al.[24] demonstrate effects of self heating on various model parameters and Vitanov et al.[11] investigated high temperature modelling of AlGaN/GaN HEMT for DC and RF characteristics. We provide a comparison of a simulated device with the experimental results along with the effect of self-heating on the AlGaN/GaN HEMT device on Si substrate. The TCAD simulation solves three fundamental equations of the semiconductor devices namely Poisson equation, electron and hole continuity equations These equations analyze electrical characteristics of the device. The high field mobility has been modeled by Transferred Electron Effect - 2 model[26] in sentaurus TCAD simulator tool and is given by following equation.[26,29] μ=. Sentaurus uses following set of equations.[26]
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