IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 9, Issue 3 Ver. I (May – Jun. 2014), PP 20-29 www.iosrjournals.org www.iosrjournals.org 20 | Page Quantum Modeling of Enhanced Gate Control in a Nanoscale InAlAs/InGaAs DG-HEMT for millimeter-wave Applications Neha Verma 1 , Mridula Gupta 2 , Enakshi Khular Sharma 3 , R.S. Gupta 4 , Jyotika Jogi 1 1 (Microelectronics Research Laboratory, Department of Electronic Science, A.R.S.D College, University of Delhi South Campus, New Delhi-110021, India) 2 (Semiconductor Device Research Laboratory, Department of Electronic Science, University of Delhi South Campus, New Delhi-110021, India) 3 (Department of Electronic Science, University of Delhi South Campus, New Delhi-110021, India) 4 (Department of Electronics and Communication Engineering, Maharaja Agrasen Institute of Technology, New Delhi-110086, India) Abstract : This paper presents quantum model for nanoscale InAlAs/InGaAs double heterostructure double gate HEMT (DG-HEMT) accounting enhanced gate control for millimeter-wave applications. The eigenenergies obtained for different gate voltages has been used to calculate the corresponding quantum electron density in the channel and is employed to calculate various device characteristics. The obtained results have been compared with the simulated results obtained from quantum moments model and are found to be in good agreement. Keywords: cut-off frequency, double-gate HEMT (DG-HEMT), electron density, quantum effects, separate gate. I. Introduction InAlAs/InGaAs HEMTs have become the most promising devices for high frequency microwave and millimeter-wave applications in military communication, remote imaging, real-time signal processing and MMICs [1-3]. They are also increasingly being used in high frequency products like mobile phones, satellite television, receivers and radar equipment. It is well established by now that the key to improve microwave performance lies in shrinking the gate length [4] and simultaneously maintaining a high aspect ratio to avoid short channel effects. But this scaling rule posed a physical limit on conventional HEMT structures and resulted in new device structure as a DG-HEMT, fabricated by transferred substrate technique [5-6], that not only minimized the short channel effects but also provided a better charge control through the second gate. Considering that DG-HEMTs have extensive use in microwave applications and particularly with the continual shrinking of device dimensions to nanoscale, where quantum effects are dominant and cannot be overlooked, accurately modeling the various RF-parameters becomes imperative. In a double heterostructure DG-HEMT under consideration, there are two identical heterostructures forming two 2-DEGs (two dimensional electron gas) and resulting in symmetric double quantum wells wherein the perpendicular motion is constrained due to quantization. These two 2-DEGs formed in the nanoscale channel have been treated independently and the net device current was taken as twice that of a single channel, ignoring the interaction between the two quantum wells [7]. The authors in this paper treat the double triangular quantum wells (DTQW) in the channel as a system in order to evaluate the various device performance characteristics. The distribution of electrons in the channel controlled by the two gate potentials applied on either sides of the channel is calculated using the eigenenergies obtained by solving 1D time-independent Schrodinger equation for the potential profile in the channel. The various device characteristics comprising drain characteristics (I D -V DS ), transfer characteristics (I D -V GS ), output conductance (g d ), transconductance (g m ), gate-to- source capacitance (C GS ) and finally the cut-off frequency (f T ) for 100 nm In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As DG-HEMT have been evaluated to study the enhanced gate control. The analytical results have been compared with the simulated results obtained from quantum moments model available in SILVACO 3D ATLAS Device simulator [8] and are found to be in good agreement. II. Model The structure of nanoscale symmetric In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As DG-HEMT with various device dimensions and doping concentrations is shown in Fig. 1. The different parameters used in the present analysis are also given in TABLE I. As can be seen from Fig. 1, the structure has two symmetric heterostructures