3D Simulation and Optimization of Characteristics of Al0.1Ga0.9N/In0.2Ga0.8N High Electron Mobility Transistor with B0.03Ga0.97N Back-Barrier Layer

The objective of this paper is to simulate the effect of a BGaN back-barrier on performances of a high electron mobility transistor (HEMT) based on AlGaN/InGaN, by using TCAD 3D Silvaco simulator. We simulate some DC and AC characteristics; we note that with only 60 nm BGaN back-barrier layer and 3% of boron in BGaN, HEMT shows improvement of 33.34% in the maximum drain current, 64.7 % in the transconductance, 19% in the threshold voltage, 50% the drain-induced barrier lowering, 34.67% in the subthreshold swing, 20% in the breakdown voltage, 10.18% in the cut-off frequency, 12% in the maximum oscillation frequency, and record high ION/IOFF of over 10 12.9 .


Introduction
The synthesis The development of civil and military communication systems, such as radar or mobile telecommunications, requires electronic components capable of generating high power levels in the microwave domain 1 New technologies are being explored to meet these two operating criteria. The high electron mobility eld effect transistor (HEMT), combined with wide band gap semiconductors such as Gallium Nitride, appears to be an excellent candidate for this type of application. 2 In fact, this HEMT based on AlGaN/InGaN heterostructure has both a high density of carriers con ned to the heterojunction and high electronic mobilities. Cut-off frequencies up to several tens of gigahertz are also obtained.
Exploring new materials and their properties is one of the most important things to expand the range of applications. In most cases, this translates into new band gap gaps or network parameters that dictate the mechanical, electrical, or optical behavior of a device. 3 It allows for band engineering and to obtain a new wavelength or new electrical properties. Among the nitride-based semiconductors that have a wide band gap, a new class of materials has emerged based on the boron alloy, electrochemical lms, BGaN alloy is a new material that has not been studied very much until now. Recently, a Japanese team has shown the possibility of developing the BGaN ternary by incorporating a small molar fraction of boron into GaN (up to 1% boron) 4 Beyond this small percentage, the fundamental di culty is to avoid phase separation GaN-BN in which the alloy is no longer formed, rich zones in boron or rich in gallium appear in the layer.
Our work ts into this context; it consists in simulating the electrical performances of a AlGaN/InGaN HEMT which contains a boron gallium nitride (BGaN) back-barrier layer under the (InGaN) channel layer and comparing them to those of the transistor without this back-barrier layer.
Proposed structure and simulation model The ideal Several works exist on the AlGaN/InGaN HEMT structures but very little on the AlGaN/InGaN/BGaN HEMT. The purpose of our work is therefore to make a comparison between these two structures, we use Silvaco software under the module DevEdit 3D and Atlas to obtain different characteristics. where ε is the electrostatic potential, ψ is the local permittivity, and ρ is the local space charge density.
The continuity equations describe the temporal variations of the charge densities (electrons, holes); they are de ned by the Eq (2) and (3).
where n and p are the electron and hole concentrations, Jn and Jp are the electron and hole current densities, Gn and Gp are the generation rates for electrons and holes, Rn and Rp are the recombination rates for electrons rates for electrons and holes, and q is the magnitude of the charge on an electron.
The basic band parameters for de ning heterojunctions in Blaze are bandgap parameter, electron a nity, permittivity, and mobility.
The Energy band gap of the B x Ga 1-x N depending on the boron fraction can be approximated using a modi ed Vegard's law including the bowing parameter (b) 8, 9 , in addition to the linear interpolation; this is given by Eq. (4).  The transfer characteristic is shown in Fig. 3. we obtain a threshold voltage (Vth) of about −4.25 V and − 3.5 V, respectively for HEMT with and without BGaN back-barrier layer.  The incorporation of boron in GaN increases the resistivity of the BGaN back-barrier layer and improves the mobility of the carriers in the active layer; this layer makes the buffer layer more resistant so that the leakage of electrons from the channel to the substrate becomes more di cult, it serves as an electrostatic barrier.
Where we notice that without the back-barrier (a)-HEMT, the Ion = 10 -2.2 A and the Ioff =10 -7.8 A resulting in an Ion/Ioff ratio of 10 5.5 , so the (b)-HEMT exhibit an Ion/Ioff ratio better than the (a)-HEMT because of the BGaN Back-barrier.We get an Ion / Ioff ratio that is almost 10 7.4 times larger for (a)-HEMT.
The sub-threshold swing (SS) is determined on the log (Ids) characteristic as a function of Vgs. It corresponds to the gate-source voltage to be applied to reduce the drain current by one decade. It is obtained for Vgs values close to the pinch, and is de ned in mV/dec (variation of Vgs when Ids is divided by ten).  For the (b)-HEMT with the back-barrier, the gate-leakage current is invariant with the gate bias, the device offers a gate leakage only of 7.10 -35 A at -0.2 V, where we notice that with the back-barrier (b)-HEMT, the gate leakage only of 7.10 -35 A. This extremely low value is evident to indicate the high quality of the device The frequency device performance is studied by small-signal AC analysis, the cut-off frequency (f t ) and the maximum oscillation frequency (f max ). We study the in uents of a BGaN back-barrier on characteristics RF of an high electron mobility transistor (HEMT). Fig. 8a  When the boron added , the BGaN ternary compound becomes more resistive and opposes better the leakage of the charge carriers towards the substrate. The DC and AC properties were compared and investigated, our results allow us to conclude that device performance continuously augment with of B 0.03 Ga 0 . 97 N back-barrier layer. It is found that the saturation drain current , the peak transconductance , SS, DIBL, the cut-off frequency (ft), the maximum oscillation frequency (fmax) and rapport ION/IOFF increases identically with B 0.03 Ga 0.97 N back-barrier layer.
It can be said that a layer of BGaN can be very resistive with only a few percent boron, which could be very interesting for devices such as HEMTs, the proposed device structure is promising for highperformance and high-speed applications.