e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:02/Issue:06/June -2020
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TCAD SIMULATION OF ALGAN/INALGAN/GAN HEMTS (HIGH ELECTRON MOBILITY TRANSISTORS) N. Ramkumar*1, Kotha S V Madhav*2, K. Karthik*3, S. Ruby*4, D. Mahesh*5 *1
Assistant Professor, Department of Electronics and Communication Engineering, Anil Neerukonda Institute of Technology & Sciences, Visakhapatnam, India. *2,3,4,5
Students, Department of Electronics and Communication Engineering, Anil Neerukonda Institute of Technology & Sciences, Visakhapatnam, India
ABSTRACT We report microwave and DC performance of a novel 50 nm Quaternary based AlGaN/InAlGaN/GaN (HEMTs) High Electron Mobility Transistor with Al2O3 passivation and T-gate on SiC substrate. TCAD is used for simulating the proposed HEMT structure. A peak drain current density(Ids) is shown at the regrown n++ GaN source/drain ohmic contacts of 2.9 A/mm with low on-resistance 0.49 Ω.mm. A record power gain (fmax) and current gain cut-off frequencies (ft) obtained are 425GHz and 310GHz respectively. These are achieved by substantial reduction in the device extrinsic and intrinsic parasitic capacitance and resistances. Here AlGaN is used as back barrier-structure to the 7nm thin In0.13Al0.83Ga0.04N (Quaternary barrier) layer in order to compensate the short channel effects with 38V improved breakdown voltage. For next generation, the prominent DC characteristic along with microwave characteristic of proposed HEMT device is appropriate candidate for electronic high power millimeter wave applications. Keywords: Quaternary barrier; double hetero-junction; millimeter wave; cut-off frequency; breakdown voltage
I.
INTRODUCTION
The expedient performance of GaN based HEMTs such as low on resistance, high breakdown field, high current density; high electron velocity, high power amplification and high thermal stability empowered the progress of high power and high speed millimeter wave electronics and photonic applications [1-34]. Over the past two decades, extensive research works has been carried out for significant improvements in operating frequency of the GaN-based HEMT. Conventional AlGaN/GaN HEMT with 0.25 µm gate length shown its microwave performance f t/fmax of 82/103 GHz [15]. T. Palacio et. al. fabricated 100 nm AlGaN/GaN HEMT with InGaN back-barrier and the device shown excellent ft/fmax of 153/230 GHz [16]. 150 nm recessed gate InAlN/GaN HEMT recorded f t/fmax of 70/105 GHz with 29 V breakdown voltage [17]. Dong Seup Lee et. al. reported f t/fmax of 245/13 GHz for 30 nm InAlN/GaN HEMT [18]. Fully passivtaed InAlN/GaN HEMT significantly improves the microwave performance f t/fmax of 205/220 GHz [19]. Jinwook W et. al. demonstrated high transconductance results from recessed gate InAlN/GaN with Al 2O3 passivation layer [20]. In spite of short channel effects, 30 nm gate length InAlN/GaN HEMT recorded ft/fmax of 373/28 GHz [21]. Lattice matched In0.17Al0.83N/GaN HEMTs demonstrated excellent high frequency performance than conventional AlGaN/GaN HEMTs [17-21]. However, due to interface roughness scattering, improvement in 2-D electron gas mobility in InAlN/GaN based HEMTs remains challenging [30] by immiscibility between AlN and InN. Existence of narrower immiscibility, Quaternary barrier In 0.16Al0.74Ga0.10N has been demonstrated high carrier mobility (μ> 1800 cm2/V · s) and high electron density (ns ~ 1.8 × 1013 cm−2) [22,23,24,25,29,32,33]. In recent years, the effort of nitride researchers are directed towards lattice matched In0.16Al0.74Ga0.10N/AlN/GaN heterostructures. To obtain high ft/fmax with simultaneous improvement in breakdown voltage for next generation high power millimeter wave electronics, it is necessary to optimize the device structure for low gate resistance, parasitic capacitances and minimum gate leakage current. In this research work, a novel 50 nm T-gate lattice matched quaternary barrier In0.16Al0.74Ga0.10N/GaN HEMT is studied and it’s DC and microwave characteristics are presented. Lg 50 nm InAlGaN/GaN HEMTs on SiC substrate is exhibited a record ft/fmax of 310/425 GHz with simultaneous high output current density of (I ds) of 2.9 A/mm and breakdown voltage of 48 V. AlGaN back barrier-structure along with a very thin 7nm InAlGaN barrier effectively mitigates the short channel effect (DIBL= 80 mV/V) with improved breakdown voltage of 48 V
II.
DEVICE STRUCTURE AND BANDGAP DIAGRAM
In0.16Al0.74Ga0.10N/AlN/GaN/AlGaN double heterostructures on SiC schematic diagram is displayed in Fig.1 (a). The proposed device made up of 7 nm In 0.16Al0.74Ga0.10N quaternary barrier material, 1 nm wide bandgap AlN spacer layer (6.02 eV), GaN channel and Al0.08Ga0.92N back-barrier. The drain and source regions are formed by Si doped n++ GaN www.irjmets.com
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