• T R Lenka

      Articles written in Pramana – Journal of Physics

    • AlGaN/GaN-based HEMT on SiC substrate for microwave characteristics using different passivation layers

      T R Lenka A K Panda

      More Details Abstract Fulltext PDF

      In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si3N4 and SiO2 passivation layers using technology computer aided design (TCAD). THe two-dimensional electron gas (2DEG) transport properties are discussed by solving Schödinger and Poison equations self-consistently resulting in various subbands having electron eigenvalues. From DC characteristics, the saturation drain currents are measured to be 600 mA/mm and 550 mA/mm for Si3N4 and SiO2 passivation layers respectively. Apart from DC, small-signal AC analysis has been done using two-port network for various microwwave parameters. The extrinsic transconductance parameters are measured to be 131.7 mS/mm at a gate voltage of $V_{gs} = -0.35$ V and 114.6 mS/mm at a gate voltage of $V_{gs} = -0.4$ V for Si3N4 and SiO2 passivation layers respectively. The current gain cut-off frequencies $(f_{t})$ are measured t be 27.1 GHz and 23.97 GHz in unit-gain-point method at a gate voltage of -0.4 V for Si3N4 and SiO2 passivation layers respectively. Similarly, the power gain cut-off frequencied $(f_{max})$ are measured to be 41 GHz and 38.5 GHz in unit-gain-point method at a gate voltage of -0.1 V for Si3N4 and SiO2 passivation layers respectively. Furthermore, the maximum frequency of oscillation or unit power gain (MUG = 1) cut-off frequencies for Si3N4 and SiO2 passivation layers are measured to be 32 GHz and 28 GHz respectively from MUG curves and the unit current gain, $|h_{21}| = 1$ cut-off frequencies are measured to be 140 GHz and 75 GHz for Si3N4 and SiO2 passivation layers respectively from the $abs |h_{21}|$ curves. HEMT with Si3N4 passivation layer giver better results than HEMT with SiO2 passivation layer.

    • Impact of oxide thickness on gate capacitance – Modelling and comparative analysis of GaN-based MOSHEMTs

      Kanjalochan Jena Raghunandan Swain T R Lenka

      More Details Abstract Fulltext PDF

      In this paper, we have developed a mathematical model to predict the behaviour of gate capacitance and threshold voltage with nanoscale variation of oxide thickness in AlInN/GaN and AlGaN/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT). The results obtained from the model are compared with the TCAD simulation results to validate the model. It is observed that AlInN/GaN MOSHEMT has an advantage of significant decrease in gate capacitance up to 0.0079 pF/𝜇m2 with increase in oxide thickness up to 5 nm as compared to conventional AlGaN/GaN MOSHEMT. This decrease in gate capacitance in AlInN/GaN MOSHEMT reduces the propagation delay and hence improves the RF performance of the device.

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