Sandeep Dhakad - Academia.edu (original) (raw)

Papers by Sandeep Dhakad

Research paper thumbnail of Influence of High-K and Low-K Dielectrics on Drain Current of GaN HEMTs

Computational Mathematics, Nanoelectronics, and Astrophysics, 2021

Research paper thumbnail of AlGaN/GaN HEMT Based pH Sensor

Springer Proceedings in Physics, 2019

The sensitivity of GaN HEMTs upon exposure of the gate area to phosphate buffer solution (PBS) ha... more The sensitivity of GaN HEMTs upon exposure of the gate area to phosphate buffer solution (PBS) has been explored. Output drain characteristic of the device reveals that the drain current decreases linearly with pH values. Higher pH contains less H + concentration and which is tends to lower the drain current. A high sensitivity of 4.32 µA/mm-pH at V ds = +1 V is obtained.

Research paper thumbnail of Development of GaN HEMTs Based Biosensor

Springer Proceedings in Physics, 2019

In this paper, we report on the development of GaN HEMTs for sensing/biosensing applications. Var... more In this paper, we report on the development of GaN HEMTs for sensing/biosensing applications. Various process steps are optimized at each stages for the development of device. Device shows the 0.5 A/mm drain current, 160 ms/mm transconductance and −4.2 V pinch of voltage for 50 µm Lsd. Devices are packaged for the detection of salt and BPA. Various molar solutions of salt are tested on gateless devices and surprisingly, it is able to detect even the femto molar level of salt. As endocrine disruptors, BPA (Bisphenol A) is tested on gated devices which shows change of about 760 µA in drain current.

Research paper thumbnail of Refined isolation techniques for GaN-based high electron mobility transistors

Materials Science in Semiconductor Processing, 2018

This work investigates the Ar + /N + based ion implantation and Ar based reactive ion etching (RI... more This work investigates the Ar + /N + based ion implantation and Ar based reactive ion etching (RIE) techniques for device isolation. A comparison of ion implantation technique with three ion energies (20/35/65 keV) and 4 energies (20/35/65/160 keV) of Ar + and N + with different ion doses for isolation was reported. Use of 4 energy ion implantation provided better isolation. Ar based single and dual step reactive ion etching process was also explored for the mesa isolation of GaN HEMTs. The etch rate increases (44.7%) significantly after mixing of Ar gas directly with BCl 3 : Cl 2 combination. Hence, the Ar addition in the single step etching proved to be more beneficial as compared to the double step etching technique.

Research paper thumbnail of Optimization of ohmic contacts on thick and thin AlGaN/GaN HEMTs structures

Superlattices and Microstructures, 2017

In this paper, we address the Ohmic contacts comparison and optimization on both thin (18 nm) and... more In this paper, we address the Ohmic contacts comparison and optimization on both thin (18 nm) and thick (25 nm) AlGaN/GaN HEMTs structures. In the conventional metallization scheme of Ti/Al/Ti/Au, several stacks based on Ni, Cr, and Pt metals replacing the middle Ti were tested and compared. Specific Contact Resistance (ρ c) strongly depends on the stack ratio. For a particular, stack ratio of 1:5:2:3 tested on thick AlGaN based HEMTs, Cr stack exhibited the least ρ c value of 5x10-5 Ω-cm 2 while the ρ c value doubled for Pt and increased by 4 times for Ni. But the morphology comparison shows that Ni is the best choice. Therefore the Ni-based stack was further optimized for low contact resistance. In the optimization process, pre-metallization surface treatments were altered along with the stack ratios. The stack ratio of 1:5:2:2.5 has resulted in lowest specific contact resistance value of 6×10-6 ohm-cm 2. Different Ni-based stacks with ratio variations were then deposited and compared for thick and thin AlGaN/GaN HEMTs structures. The same value of ρ c was recorded on both thick and thin structures as long as the Ni proportion in the stack is low. With an increase in the Ni proportion, ρ c was found to be increased dramatically for thin AlGaN/GaN HEMTs.

Research paper thumbnail of Influence of High-K and Low-K Dielectrics on Drain Current of GaN HEMTs

Computational Mathematics, Nanoelectronics, and Astrophysics, 2021

Research paper thumbnail of AlGaN/GaN HEMT Based pH Sensor

Springer Proceedings in Physics, 2019

The sensitivity of GaN HEMTs upon exposure of the gate area to phosphate buffer solution (PBS) ha... more The sensitivity of GaN HEMTs upon exposure of the gate area to phosphate buffer solution (PBS) has been explored. Output drain characteristic of the device reveals that the drain current decreases linearly with pH values. Higher pH contains less H + concentration and which is tends to lower the drain current. A high sensitivity of 4.32 µA/mm-pH at V ds = +1 V is obtained.

Research paper thumbnail of Development of GaN HEMTs Based Biosensor

Springer Proceedings in Physics, 2019

In this paper, we report on the development of GaN HEMTs for sensing/biosensing applications. Var... more In this paper, we report on the development of GaN HEMTs for sensing/biosensing applications. Various process steps are optimized at each stages for the development of device. Device shows the 0.5 A/mm drain current, 160 ms/mm transconductance and −4.2 V pinch of voltage for 50 µm Lsd. Devices are packaged for the detection of salt and BPA. Various molar solutions of salt are tested on gateless devices and surprisingly, it is able to detect even the femto molar level of salt. As endocrine disruptors, BPA (Bisphenol A) is tested on gated devices which shows change of about 760 µA in drain current.

Research paper thumbnail of Refined isolation techniques for GaN-based high electron mobility transistors

Materials Science in Semiconductor Processing, 2018

This work investigates the Ar + /N + based ion implantation and Ar based reactive ion etching (RI... more This work investigates the Ar + /N + based ion implantation and Ar based reactive ion etching (RIE) techniques for device isolation. A comparison of ion implantation technique with three ion energies (20/35/65 keV) and 4 energies (20/35/65/160 keV) of Ar + and N + with different ion doses for isolation was reported. Use of 4 energy ion implantation provided better isolation. Ar based single and dual step reactive ion etching process was also explored for the mesa isolation of GaN HEMTs. The etch rate increases (44.7%) significantly after mixing of Ar gas directly with BCl 3 : Cl 2 combination. Hence, the Ar addition in the single step etching proved to be more beneficial as compared to the double step etching technique.

Research paper thumbnail of Optimization of ohmic contacts on thick and thin AlGaN/GaN HEMTs structures

Superlattices and Microstructures, 2017

In this paper, we address the Ohmic contacts comparison and optimization on both thin (18 nm) and... more In this paper, we address the Ohmic contacts comparison and optimization on both thin (18 nm) and thick (25 nm) AlGaN/GaN HEMTs structures. In the conventional metallization scheme of Ti/Al/Ti/Au, several stacks based on Ni, Cr, and Pt metals replacing the middle Ti were tested and compared. Specific Contact Resistance (ρ c) strongly depends on the stack ratio. For a particular, stack ratio of 1:5:2:3 tested on thick AlGaN based HEMTs, Cr stack exhibited the least ρ c value of 5x10-5 Ω-cm 2 while the ρ c value doubled for Pt and increased by 4 times for Ni. But the morphology comparison shows that Ni is the best choice. Therefore the Ni-based stack was further optimized for low contact resistance. In the optimization process, pre-metallization surface treatments were altered along with the stack ratios. The stack ratio of 1:5:2:2.5 has resulted in lowest specific contact resistance value of 6×10-6 ohm-cm 2. Different Ni-based stacks with ratio variations were then deposited and compared for thick and thin AlGaN/GaN HEMTs structures. The same value of ρ c was recorded on both thick and thin structures as long as the Ni proportion in the stack is low. With an increase in the Ni proportion, ρ c was found to be increased dramatically for thin AlGaN/GaN HEMTs.