GaN HEMT for future high power RF applications

Accepted Manuscript Regular paper DC and Microwave Characteristics of Lg 50nm T-Gate InAlN/AlN/GaN HEMT for Future High Power RF Applications P. Murugapandiyan, S. Ravimaran, J. William PII: DOI: Reference:

S1434-8411(17)30048-1 http://dx.doi.org/10.1016/j.aeue.2017.05.004 AEUE 51875

To appear in:

International Journal of Electronics and Communications

Received Date: Accepted Date:

9 January 2017 4 May 2017

Please cite this article as: P. Murugapandiyan, S. Ravimaran, J. William, DC and Microwave Characteristics of Lg 50nm T-Gate InAlN/AlN/GaN HEMT for Future High Power RF Applications, International Journal of Electronics and Communications (2017), doi: http://dx.doi.org/10.1016/j.aeue.2017.05.004

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DC and Microwave Characteristics of Lg 50nm T-Gate InAlN/AlN/GaN HEMT for Future High Power RF Applications P.Murugapandiyana , S.Ravimaranb , J.Williamc a

b

Assistant Professor, Department of Electronics and Communication Engineering, Ariyalur Engineering college ,Melakaruppur,Tamilnadu-India.

Professor, Department of Electrical and Computer Science, M.A.M College of Engineering, Trichy-India.

c

Professor, Department of Electronics and Communication Engineering, M.A.M College of Engineering and Technology, Trichy-India. E-mail: [email protected]

Authors

P.Murugapandiyan has received his B.E in Electronics and Communication Engineering from Anna University , Chennai, Tamil Nadu, India in 2008 and he received Master of Engineering in VLSI Design from Anna University, Chennai, Tamil Nadu, India in the year 2013. He is pursuing Ph.D at Anna University, Chennai, Tamilnadu- India. Now he is working as Assistant Professor in the Department of Electronics and Communication Engineering, Ariyalur Engineering College Melakaruppur, Tamilnadu - India. His research focuses on modelling and simulation of III–N compound semiconductor materials and devices for future high speed with high power MMIC applications.

S.Ravimaran , Principal and Professor in Computer Science and Electrical Engineering department of the M.A.M. College of Engineering, Tamil Nadu,India and he has received his B.E. in computer science and engineering from National Institute of Technology, Tiruchirapalli, India in 1997 and his M.E. Computer science and engineering from Anna University, Chennai, Tamil Nadu, India in 2004. He has done his Ph.D. in Data and Transaction Management Using Surrogate Objects in Distributed Mobile Systems fromAnna University Chennai, India in 2013. His research interests are High speed wireless Communication Networks and wide band attenna design for MMIC RF applications.

J.William, Principal and Professor in Electronics and Communication Engineering department of the M.A.M. College of Engineering and Technology, Tamil Nadu-India and he has received Doctor of Philosophy in the area of ULTRA WIDEBAND ANTENNA, Pondicherry Central University, Pudhucherry, India, in the year 2011 and Master of Technology with the specialization of Communication Systems at NIT, Trichy in the year 2006. His research interests are GaN based High power amplifier and oscillator design for milli meter wave high power applications.

DC and Microwave Characteristics of Lg 50nm T-Gate InAlN/AlN/GaN HEMT for Future High Power RF Applications Abstract The DC and microwave characteristics of Lg=50 nm T-gate InAlN/AlN/GaN High Electron Mobility Transistor (HEMT) on SiC substrate with heavily doped n+ GaN source and drain regions have demonstrated using Synopsys TCAD tool. The proposed device features an AlN spacer layer, AlGaN back-barrier and SiN surface passivation. The proposed HEMT exhibits a maximum drain current density of 1.8 A/mm, peak transconductance (gm) of 650 mS/mm and ft/fmax of 118/210 GHz. At room temperature, the measured carrier mobility, sheet charge carrier density (ns) and breakdown voltage are 1195 cm2/Vs, 1.6 x 1013 cm-2 and 18 V respectively. The superlatives of the proposed HEMTs are bewitching competitor for future monolithic microwave integrated circuits (MMIC) applications particularly in W-band (75-110 GHz) high power RF applications. Keywords HEMT, 2DEG, Back-barrier, Cut-off frequency, DC and Microwave characteristics 1. Introduction To reinforce the next generation high power mixed signal monolithic microwave integrated circuits (MMIC), there is a huge demand for high power microwave transistors. In recent years, GaN-based High Electron Mobility Transistors (HEMTs) have attracted enormous attention for future deployment of high power RF applications, which offers high output power density than other materials systems such as GaAs or InP at high frequency operation. The unique combination of larger band gap (3.44 eV), breakdown field (3.3 x 106 V/cm), higher saturation velocity (2.7 x 107 cm/S), good thermal conductivity 1.95 Wcm-1C-1 and higher mobility (µ n = 2000 and µ h = 200 cm2/Vs) of GaN based HEMTs are useful in high power sub-millimeter wave RF applications, such as next generation wireless communications, development of satellite telecommunication systems, high power amplifiers for radar and space research, microwave image sensing and low noise wide bandwidth amplifiers design. Recently the lattice-matched InAlN/GaN heterojunction high electron mobility transistors (HEMTs) are of great interest for high power switching and RF applications because of their high breakdown voltage, high current density, cut-off frequencies, and good thermal stability [1-4,14-36]. The limitation of AlGaN/GaN HEMT has been reached now in particular for the bottom part of the mm-wave spectrum (~300). Furthermore, the unavoidable strain induced at the interface because of lattice mismatch between GaN and AlGaN limits the Al contents in the barrier to about 30% and therefore the 2DEG density limited to ~1013 cm-2. As a consequence, the maximum current density is limited to 1 A/mm. The presence of strain has been identified as a source of failure for these devices [5,6]. Lattice matched InAln/GaN HEMTs present several advantages with respect to AlGaN/GaN. The Lattice matched InAlN/GaN HEMTs allow for a more efficient downscaling of the transistor dimensions,

making easier to achieve cut-off frequencies more than 200 GHz [8]. InAlN/GaN HEMT have been shown to demonstrate a maximum current density of 2 A/mm [9]. Therefore InAlN/GaN based HEMTs are considered to be ideal candidates for high power applications at frequencies more than 100
. Besides the remarkable potential for high power and high-frequency applications, InAlN/GaN HEMT has also been demonstrated for good thermal stability at 1000°  [11]. However, despite the great potentials of InAlN/GaN HEMTs, these devices are suffering from large leakage currents and consequently, low breakdown voltages are reported [12]. The ohmic contacts were characterized to reduce the contact resistance of ~0.3 .

[13]. Devices for high-temperature operation requires lower leakage currents because higher leakage currents strongly degrades the operating temperature of HEMTs. Finally high performance HEMTs were reported on SiC substrate. InAlN/GaN HEMTs offers a better carrier confinement in the 2DEG than conventional AlGaN/GaN based HEMT due to larger spontaneous polarization between the barrier and channel [6]. To reduce the alloy disorder scattering at the InAlN/GaN interface, a very thin AlN spacer layer is placed in between which improves the sheet charge carrier density in 2DEG region. The higher cut-off frequency is obtained by appropriate scaling of gate length and device design. However, the associated breakdown voltage (VBR) of the device deteriorates as the device is scaling down. The lower breakdown voltage of the HEMTs limits the dynamic range of the device operation. During the last few years InAlN material is used as the top barrier for ultra-scaled devices to achieve a high 2DEG density (>1013 cm-2) with a smaller thickness without the need of modulation doping and also it greatly mitigates the gate leakage current with the help of large barrier height. To enhance both the ft and fmax with high breakdown voltage simultaneously, proper device design and scaling is required. For achieving high ft and fmax, the key parameters such as gate-drain capacitance (Cgd), drain conductance (gd), contact resistances (Rs &Rd), device on resistance (Ron) and gate resistance (Rg) of the transistor are to be minimized. Also the transconductace (gm) and drain current density (Ids) of the HEMTs have to be maximized. The T-shaped gate is found to be very much effective in reducing gate resistance and gate to drain capacitance [37-41]. In this article, we have proposed a novel InAlN/GaN high electron Mobility Transistor (HEMT) with AlGaN back-barrier. The device features T-shaped gate associated with SiN passivation to minimize the gate resistance (Rg) and parasitic capacitances particularly Cgd. Moreover, the AlN spacer layer and AlGaN back-barriers greatly helped to enhance the sheet carrier density in the 2DEG channel with improved carrier mobility. The device structure is simulated by using Synopsys TCAD tool. The Lg=50 nm InAlN/GaN HEMT exhibits a current gain cut-off frequency ft of 118 GHz and power gain cut-off frequency fmax of 210 GHz. The peak drain current density of 1.8 A/mm is achieved with the enhanced sheet charge carrier density of 1.6X1013 cm-2 and carrier mobility of 1190 cm2/V-s. 18 V off-state breakdown voltage (VBR) is recorded by using asymmetric gate position.

2. //  Device Structure and Bandgap Diagram: The vertical cross sectional view of InAlN/AlN/GaN HEMT with AlGaN back-barrier is shown in Fig.1. The HEMT having a gate length of 50 nm , uses a GaN cap layer of 2 nm , InAlN barrier of 3.5 nm, and a very thin 1nm AlN spacer layer. The proposed AlN spacer based HEMT with 1.5µm Al0.07Ga0.93N back-barrier attenuated the short channel effects and provides better electron confinement in 2DEG .The access and output resistance of HEMTs limits the performance of these devices, since the contact resistivity is a major part of such parasitic resistances. The heavily doped 90nm n+ GaN source/drain ohmic contacts allowed a significant reduction of the contact resistivity in proposed device. The regrown ohmic contacts have thus become a requirement for high speed GaN based HEMTs. To achieve the higher cut-off frequency, it’s desirable to reduce the gate resistance. The T-shaped schottky (Ti/Pt/Au) gate with a small footprint (50 nm length, 200 nm stem height and 500nm wide) used as gate contact. The reduction in the gate to drain space can causes the high electric field in the gate-source region which results in high Cgs and high gd. In this work, gate to source and the gate to drain distance is kept at 30 nm and 80 nm respectively to maintain a low electrostatic field in the gate-drain space channel region while maintaining enhanced breakdown voltage. 2 nm GaN cap layer associated with 2.5 nm InAlN barrier and AlN barrier material effectively mitigates the gate leakage current. On top of the GaN cap layer, 1nm Si3N4 used as passivation layer to limit the amount of electrically active traps that causes the dispersion effects. SiC is used as a substrate for the proposed device due to their excellent thermal conductivity. A 50 nm AlN is used as a nucleation layer which is situated between SiC substrate and AlGaN back-barrier which reduces the strain-induced effects because of lattice mismatch between SiC and Al0.07Ga0.93N layers.

Figure.1.Cross-sectional view (not drawn to scale) of a spacer layer-based InAlN/AlN/GaN HEMT.

Fig. 2. Conduction band diagram for InAlN/AlN/GaN/AlGaN heterostructure. The Conduction band offset diagram of InAlN/AlN/GaN/AlGaN is depicted in Fig.2. The InAlN/GaN hetero-junction benefits the high 2DEG density (~1013 cm-2) without doping and high electron mobility (~2000 cm2/V-s) because of the large conduction band discontinuity between the InAlN/GaN. The high 2DEG density is achieved by large spontaneous and piezoelectric polarization field inside the InAlN layer. The amount of 2DEG density is controlled by the thickness of the barrier layer and the Al content InAlN. To confine the induced 2DEG electron density in the channel region AlGaN back-barrier is used in our proposed structure, which also helped to enhance the breakdown voltage of the device. The induced piezoelectric polarization between AlGaN and GaN layers creates a sharp raised potential barrier is at the back of 2DEG channel. Such a sharp notch assist for confining the polarization induced charge carrier in a better manner in the channel region and also it mitigates the buffer leakage current. A very thin 1 nm wide band gap (6.01 eV) AlN spacer presented in between the barrier and channel offering the large effective conduction band offset which also contributes to higher sheet charge carrier density with enhanced electron mobility. 3. Results and Discussion In this article, we have demonstrated the DC and microwave characteristics of InAlN/AlN/GaN with AlGaN back-barrier HEMT device of 50nmX20µm device dimension. Fig.3 depicts the sheet charge carrier density variation with InAlN/AlGaN barrier thickness. A thin 3.5 nm InAlN used as barrier layer achieved a sheet carrier density of 1.6 x 1013 cm2 which is comparatively higher than with the AlGaN barrier layer and the measured mobility in the 2DEG is 1190 cm-2/Vs. Fig.4 shows the V–I characteristics of Lg=50 nm and W=20µm InAlN/AlN/GaN HEMT. The simulation result gives a supreme current density of 1.8 A/mm at Vgs=2V and the device is pinched off perfectly at Vgs=-6V. This higher current density is achieved mainly because of the enhanced mobility with greater sheet charge carrier density in 2DEG channel. The lattice-matched InAlN/GaN with 1 nm SiN spacer provides effective

conduction band offset and it reduces strain induced surface defects at the interface. Moreover, the AlGaN notch helps to provide better confinement of charge carriers in the channel and also it suppressed the buffer leakage current in the device. The breakdown voltage of the device is the most essential parameter for high power RF applications. A 18V off-state breakdown voltage is obtained from the breakdown characteristics of the proposed HEMT which is depicted in Fig.5. For very thin barrier layer, this high breakdown voltage is obtained mainly because of the asymmetric gate position associated with AlGaN backbarrier. The DC characteristic of the proposed InAlN/GaN HEMT is validated with the same Lg of 50 nm InAlN/GaN HEMT device [34].

Figure.3. Sheet charge density dependency on barrier layer thickness The transfer characteristic of the proposed HEMT is shown in Fig.6. The extracted threshold voltage of the device from the transfer characteristics is -3.8V. Fig.7 shows the transconductance variation with the gate bias voltage. The maximum transconductance of the device observed from the plot is 650 mS/mm at Vgs=3V and the associated drain voltage is 2V. The gm of the proposed HEMT is higher than the same gate length InAlN/GaN HEMT structure reported in [34]. The subthreshold and gate leakage current characteristics of Lg=50 nm and W=20µm InAlN/AlN/GaN depletion mode HEMT is shown in Fig.8. The gate leakage current depends on band gap of the barrier and channel materials. The higher band gap InAlN with AlN space layer effectively suppressed the gate leakage current in the order of 1X10 -13 A/mm at zero gate-source bias and the drain current on/off ratio is observed as >107 at Vds=2V. The gate leakage current gradually decreases with the increasing gate bias from a negative bias to zero.

Fig.4.  −  characteristics of  width of 50  , 20 . .

.!" #$ .%& ' /#$'/
('

)*+ with gate length and

Figure.5. Breakdown characteristics of /0 = 50 nm and 1 = 20 . InAlN/AlN/GaN HEMT.

Figure.6.Dependences of 34 on the gate bias of /0 = 50 nm and 1 = 20 . InAlN/AlN/GaN HEMT.

Figure.7.Transfer characteristics of of /0 = 50 nm and 1 = 20 . InAlN/AlN/GaN HEMT.

Figure.8.Subthreshold and gate leakage current characteristics of /0 = 50 nm and 1 = 20 . InAlN/AlN/GaN HEMT.

Figure.9.cut-off frequency variation with gate-source voltage of /0 = 50 nm and 1 = 20 . InAlN/AlN/GaN HEMT. The expression for ft and fmax can be written as follows; Current gain Cut-off frequency

56 =

07 /089

(1)

D GHA>?@8 .07 /089 BIJ9 AJ8KL @89 E>F9 EF8B

:;<=>?@9 A?@8 BAC

Power gain cut-off frequency 54MN =

T

OP

Where the source resistance

J9Y .Z\] V

(2)

: Q>J9 AJ@ B089 A:;OP J@ ?@8 J

J9Y .Z[\

RS = T U W + T V

V

J

W and drain resistance R = T U W + V

W . R^ and RS_ are the contact resistance and channel sheet resistance respectively.

/`a and /ab are gate to source and gate to drain spacing respectively and 1 is the width of the gate. For the proposed HEMT, the smaller gate length with large gate foot print by adopting T-shaped gate leads to drastic reduction in source/drain contact resistances. R0 is the gate access resistance and 3S represents drain conductance. Also the reduction in gate to drain capacitance 0 is essential for high frequency operation of the device.

The simulation of current gain cut-off frequency I56 K and power gain cut-off frequency (54MN K of /3 = 50  #$'/
(' )*+ is depicted in Fig.9. The device exhibited a peak ft/fmax of 118 /210
 at Vds=3V and Vgs=-1V. The obtained results are best cut-off frequencies of GaN based HEMT with high current density of 1.8 #/

simultaneously maintaining a breakdown voltage of 18V and low gate leakage current among any materials with 50 nm gate length HEMT so far from authors knowledge. This ft/fmax is achieved by drastic reduction in the contacts resistances(Rd and Rs), gate resistance (Rg) and parasitic capacitances (Cgs and Cgd) of the device mainly because of heavily doped I  +
(' K source/drain regions which has direct contacts with the channel, combined with drain /source access region, passivated device surface and T-gate structure. The recent research progress in GaN based HEMT is shown in Table.1. Table.1. Recent research progress in GaN based HEMT for high power RF applications Reference [3], 2009 [7], 2009 [14], 2016 [31],2015 [32],2015 [33],2010 [34],2014 This work

/0

0.1 . [T-gate] 0.15 . [T-gate] 70  [T-gate] 0.14 . [T-gate] 0.3 . [T-gate] 160 nm [T-gate] 50 nm [T-gate] 50  [T-gate]

34 [ f/

]

56 [
]

54MN [
]

330

102

89

1.5

675

87

65

1.6

524

162

176

1.2

421

65

100

1.4

425

55

120

1.4

350

79

113.8

1.17

477

90

140

1.8

650

118

210

 [#/

] 1.3

5. Conclusion The DC and microwave characteristics of a novel 50  T-gate InAlN/AlN/GaN with AlGaN back-barrier has been studied by using Synopsys TCAD tool. The proposed device features heavily doped (n+ GaN) source/drain regions with Si3N4 passivated device surface which helped to reduce the contact resistances and parasitic capacitances of the device to uplift the microwave characteristics of the HEMTs. Lg of 50 nm HEMT shows a ft/fmax of 118/210 GHz. The peak drain current density of 1.8 #/

is achieved by offering effective conduction band offset by using InAlN barrier material associated with back-barrier by enhancing the sheet charge carrier density in 2DEG region I1.6 ,10!& k l:K with higher carrier mobility of 1195Ik : /n ).Moreover, 18V off-state breakdown voltage (VBR) is achieved by keeping the large gate to drain separation than gate to source. This excellent DC and microwave characteristics of the proposed HEMT device makes them the most suitable candidate for future high power millimetre wave RF applications. Acknowledgement The authors acknowledge the Nanoelectronics Device Laboratory of Electronics and Communication Engineering Department of M.A.M College of Engineering, Trichy-India for providing all facility to carry out this research work. References [1] N. Sarazin, E. Morvan, M. A. di Forte Poisson, M. Oualli, C. Gaquière, O. Jardel, O. Drisse, M. Tordjman, M. Magis, and S. L. Delage, “AlInN/AlN/GaN HEMT Technology on SiC With 10-W/mm and 50% PAE at 10 GHz” IEEE Electron Device Lett, vol. 31, no. 1, january 2010 11, http://dx.doi.org/ 10.1109/LED.2009.2035145. [2] Dong Xu, K. K. Chu, J. A. Diaz, M. Ashman, J. J. Komiak, L. Mt. Pleasant, C. Creamer, K. Nichols, K. H. G. Duh, P. M. Smith, P. C. Chao, L. Dong, and Peide D. Ye, “0.1-µm Atomic Layer Deposition Al2O3 Passivated InAlN/GaN High Electron-Mobility Transistors for E-Band Power Amplifiers” IEEE Electron Device Lett . http://dx.doi.org/ 10.1109/LED.2015.2409264 [3] Haifeng Sun, Andreas R. Alt, Hansruedi Benedickter, C. R. Bolognesi,Eric Feltin, Jean-François Carlin, Marcus Gonschorek, Nicolas Grandjean, Thomas Maier, and Rüdiger Quay,“102-GHz AlInN/GaN HEMTs on Silicon With 2.5-W/mm Output Power at 10 GHz”, IEEE Electron Device Lett, http://dx.doi.org/10.1109/LED.2009.2023603. [4] Dong Xu et.al, “0.1-µm InAlN/GaN High Electron-Mobility Transistors for Power Amplifiers Operating at 71–76 and 81–86 GHz Impact of Passivation and Gate Recess” IEEE transactions on electron devices, vol. 63, no. 8, august 2016, http://dx.doi.org/10.1109/TED.2016.2579160. [5] S.Y. Parka, C. Florescaa, U. Chowdhuryb, J. L. Jimenezb, C. Leeb, E. Beamb, P. Saunierb, T. Balistrerib, and M. J. Kim. “Physical degradation of GaN HEMT devices under high drain bias reliability testing”. Microelectron. Rel., 49:478, 2009. [6] E. Zanoni,M.Meneghini, A. Chini, D.Marcon, and G.Meneghesso. “AlGaN/GaN-based HEMTs failure physics and reliability: Mechanisms affecting gate edge and Schottky junction”. IEEE Trans. Electron Devices, 60:3119, 2013. [7] Jinwook W. Chung, Omair I. Saadat, Jose M. Tirado, Xiang Gao, Shiping Guo, and Tomás Palacios, “Gate-Recessed InAlN/GaN HEMTs on SiC Substrate With Al2O3 Passivation” IEEE Electron Device Lett, vol. 30, no. 9, september 2009, http://dx.doi.org/10.1109/LED.2009.2026718. [8] S. Liu, S. Yang, Z. Tang, Q. Jiang, C. Liu, M. Wang, and K. J. Chen,“Al2O3/AlN/GaN MOS-channelHEMTs with an AlN interfacial layer,”IEEE Electron Device Lett., vol. 35, no. 7, pp. 723–725, Jul. 2014, http://dx.doi.org/10.1109/LED.2014.2322379.

[9] F.Medjdoub, J.-F. Carlin, M. Gonschorek, E. Feltin,M. A. Py, D. Ducatteau, C. Gaquiere,N. Grandjean, and E. Kohn. “Can InAlN/GaN be an alternative to high power / hightemperature AlGaN/GaN devices?” IEDM Tech. Dig., page 673, 2006. [10] Chuan-Wei Tsou, Chen-Yi Lin, Yi-Wei Lian, and Shawn S. H. Hsu “101-GHz InAlN/GaN HEMTs on Silicon With High Johnson’s Figure-of-Merit” , IEEE transactions on electron devices, vol. 62, no. 8, august 2015, http://dx.doi.org/10.1109/TED.2015.2439699. [11] D. Maier, M. Alomari, N. Grandjean, J.-F. Carlin, M.-A. Diforte-Poisson, C. Dua,A. Chuvilin, D. Troadec, C. Gaquière, U. Kaiser, S. L. Delage, and E. Kohn. “Testing the temperature limits of GaNbased HEMT devices”. IEEE Trans. Device Mater. Rel.,10:427, 2010. [12] J. Kuzmík, A. Kostopoulos, G. Konstantinidis, J.-F. Carlin, A. Georgakilas, and D. Pogany. InAlN/GaN HEMTs: A first insight into technological optimization. IEEE Trans. Electron Devices, 55:937, 2008. [13] Ronghua Wang, Guowang Li, Oleg Laboutin, Yu Cao, Wayne Johnson,Gregory Snider, Patrick Fay,Debdeep Jena, and Huili (Grace) Xing , “210-GHz InAlN/GaN HEMTs With Dielectric-Free Passivation” IEEE electron device letters, vol. 32, no. 7, july 2011. http://dx.doi.org/10.1109/LED.2011.2147753. [14] Han Tingting, Dun Shaobo, Lü Yuanjie, Gu Guodong,Song Xubo, Wang Yuangang, Xu Peng, and Feng Zhihong, “70-nm-gated InAlN/GaN HEMTs grown on SiC substrate with fT=fmax > 160 GHz” Journal of Semiconductors , Vol. 37, No. 2 February 2016, http://dx.doi.org/10.1088/16744926/37/2/024007. [15] Hyung-Seok Lee, Daniel Piedra, Min Sun, Xiang Gao, Shiping Guo, and Tomás Palacios, “3000-V 4.3mΩ · cm2 InAlN/GaN MOSHEMTs With AlGaN Back Barrier” IEEE electron device letters, vol. 33, no. 7, july 2012, http://dx.doi.org/10.1109/LED.2012.2196673. [16] E Sakalauskas, et.al “Dielectric function and optical properties of Al-rich AlInN alloys pseudomorphically grown on GaN” J. Phys. D: Appl. Phys. 43 (2010) 365102 (10pp) doi:10.1088/0022-3727/43/36/365102 [17] Qi Zhou , Shu Yang , Wanjun Chen , Bo Zhang , Zhihong Feng , Shujun Cai, Kevin J. Chen “High voltage InAlN/GaN HEMTs with nonalloyed Source/Drain for RF power applications” Solid-State Electronics 91 (2014) 19–23, http://dx.doi.org/10.1016/j.sse.2013.09.006. [18] Stefano Tirelli, Lorenzo Lugani, Diego Marti, Jean-François Carlin, Nicolas Grandjean, and C. R. Bolognesi,“AlInN-Based HEMTs for Large-Signal Operation at 40 GHz”, IEEE transactions on electron devices, http://dx.doi.org/10.1109/TED.2013.2262136. [19] Subramaniam Arulkumaran et.al “Record-low contact resistance for InAlN/AlN/GaN high electron mobility transistors on Si with non-gold metal”Japanese Journal of Applied Physics 54, 04DF12 (2015), http://dx.doi.org/10.7567/JJAP.54.04DF12. [20] Clemens Ostermaier et.al “Ultrathin InAlN/AlN Barrier HEMT With High Performance in Normally Off Operation” IEEE electron device letters, vol. 30, no. 10, october 2009, http://dx.doi.org/10.1109/LED.2009.2029532. [21] J. Guo, G. Li, F. Faria, Y. Cao, R. Wang, J. Verma, X. Gao, S. Guo, E. Beam, A. Ketterson, M. Schuette, P. Saunier,M.Wistey, D. Jena, and H. Xing. MBE-regrown ohmics in InAlN HEMTs with a regrowth interface resistance of 0.05 -¢mm. IEEE Electron Device Lett.,33:525, 2012. [22] Nanjo T, Motoya T, Imai A et al. Enhancement of drain current by an AlN spacer layer insertion in AlGaN/GaN high-electron-mobility transistors with Si-ion-implanted source/drain contacts. Japanese J Appl Phys 2011; 50: http://dx.doi.org/10.1143/JJAP.50.064101. [23] O. Ambacher et al. “ Pyroelectric properties of Al(In)GaN/GaN hetero- and quantum well structures”, J. Phys.: Condens. Matter, 14:3399, 2002. [24] Wood C, Jena D. Polarization Effects in Semiconductors. Springer-Verlag: New York, NY, USA, 2008; 43–59. [25] Khandelwal S, Fjeldly TA. A physics-based analytical model for 2DEG charge density in AlGaN/GaN HEMT device.Solid-state Electron 2012; 76:60–66. [26] Y.-F. Wu, A. Saxler, M. Moore, R. P. Smith, S. Sheppard, P. M. Chavarkar, T. Wisleder, U. K. Mishra, and P. Parikh, “30-W/mm GaN HEMTs by field plate optimization,” IEEE Electron. Device Lett., vol. 25, no. 3, pp. 117–119, Mar. 2004, http://dx.doi.org/10.1109/LED.2003.822667. [27] Xia L, Hanson A, Boles T, and Jin D. “On reverse gate leakage current of GaN high electron mobility transistors on silicon substrate”. Appl Phys Lett 2013; 102, doi: 10.1063/1.4798257. [28] Crespo, M. et.al, “High-Power Ka-Band Performance of AlInN/GaN HEMT With 9.8-nm-Thin Barrier” IEEE electron device letters, vol. 31, no. 1, January 2010, http://dx.doi.org/10.1109/LED.2009.2034875.

[29] M. Hayati,B. Akhlaghi “An extraction technique for small signal intrinsic parameters of HEMTs based on artificial neural networks” , Elsvier, AEU - International Journal of Electronics and Communications,Volume 67, Issue 2, February 2013, Pages 123– 129,http://dx.doi.org/10.1016/j.aeue.2012.07.012. [30] Hanieh Aliakbari,Abdolali Abdipour ,Rashid Mirzavand , “Accurate time-domain modeling of multifinger pHEMT transistor based on transmission line theory”, Elsvier, AEU - International Journal of Electronics and Communications, Volume 69, Issue 1, January 2015, Pages 215–225, http://dx.doi.org/10.1016/j.aeue.2014.09.007. [31] Eblabla, X. Li, I. Thayne, D. J. Wallis, I. Guiney, and K. Elgaid “High Performance GaN High Electron Mobility Transistors on Low Resistivity Silicon for X-Band Applications” IEEE Electron. Device Lett, vol. 36, NO. 9, September 2015. DOI:10.1109/LED.2015.2460120. [32] Robert C. Fitch et.al. “Implementation of High-Power-Density X-Band AlGaN/GaN High Electron Mobility Transistors in a Millimeter-Wave Monolithic Microwave Integrated Circuit Process” IEEE Electron. Device Lett, vol. 36, NO. 10, October 2015. DOI:10.1109/LED.2015.2474265. [33] A. Crespo et.al. “High-Power Ka-Band Performance of AlInN/GaN HEMT With 9.8-nm-Thin Barrier” IEEE Electron. Device Lett, vol. 31, NO. 1, January 2010. DOI:10.1109/LED.2009.2034875. [34] Anna Malmros et.al. “Evaluation of an InAlN/AlN/GaN HEMT with Ta-based ohmic contacts and PECVD SiN passivation” Phys.Status Solidi C 11,No.3–4,924–927(2014)/DOI:0.1002/pssc.201300320 [35] B.K. Jabalin, A. Shobha, D. Nirmal, et al., “Unique model of polarization engineered AlGaN/GaN based HEMTs for high power applications”, Superlattices and Microstructures, Vol. 78, P. 210-223, 2015. [36] B.K. Jabalin, A. Shobha, D. Nirmal, et al., “The influence of high-k passivation layer on breakdown voltage of Schottky AlGaN/GaN HEMTs”, Microelectron. J., Vol. 46, No. 12, 2015. [37] J. Ajayan, D. Nirmal, A Review of InP/InAlAs\InGaAs Based Transistors For High Frequency Applications, Superlattices and Microstructures, Vol. 86, No. 10, P. 1-19, October, 2015. [38] J. Ajayan, and D. Nirmal, “20 nm High Performance Enhancement Mode InP HEMT with Heavily Doped S/D Regions for Future THz Applications”, Superlattices and Microstructures, Vol. 100, No. 15, P. 526-534, 2016. [39] J. Ajayan, and D. Nirmal, “20nm Enhancement Mode Metamorphic GaAs HEMT with Highly Doped InGaAs Source/Drain Regions for High Frequency Applications”, International Journal of Electronics, Taylor & Francis Group, Vol.104, No. 3, P.504-512, 2017. [40] J. Ajayan, and D. Nirmal, “20nm T-Gate Composite channel Enhancement-Mode Metamorphic HEMT on GaAs Substrates For Future THz Applications”, Journal of Computational Electronics, Springer, Vol. 15. No. 4, P. 1291-1296, 2016. [41] J. Ajayan, and D. Nirmal, “22 nm In0.75Ga0.25As Channel Based HEMTs on InP/GaAs Substrates For Future THz Applications”, Journal of Semiconductors, Vol. 38, No. 4, P. 044001-1, 2017.