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In this paper, we showcase our investigation regarding the effect of acceptor traps in GaN buffer and AlGaN barrier layers on the leakage current and current collapse in GaN high-electron-mobility transistors. The dependence of current collapse and leakage current on the density and energy level of traps is carefully considered. With an increase in trapping density from 1015 cm−3 to 1018 cm−3, the leakage current was significantly reduced from 80.2% to 1.76% in the buffer layer and 95% to 12.6% in the barrier layer, while the current collapse increased from 6% to 89.8% in the buffer layer and 0.3% to 17.5% in the barrier layer. The effects of current collapse and leakage were more noticeable in the buffer layer than in the barrier layer. Different energy levels (0.75 eV, 1.8 eV, and 2.85 eV) of acceptor traps were likewise studied. It was demonstrated that high-energy traps induced a lower amount of leakage, while the current collapse was greater. Based on these results, a balanced trade-off between the current collapse and the leakage current is proposed.

We have investigated the characteristics of pH and salinity sensor derived from the gated AlGaN/GaN high-electron mobility transistor (HEMT) structures in phosphate buffer saline (PBS) and aqueous salt solutions (NaCl + DI). In deionized (DI) water, the HEMT device showed good drain ${I}$ – ${V}$ characteristics, which is very close to the output characteristics of the typical HEMT structures subjected to the air. We observed a significant change in the output drain characteristics curves concerning to the variation in the pH values of PBS solutions, signifying the subsequent potential variation at the AlGaN surface. The output drain current recorded at ${V}_{\text {ds}}= +1$ V was linearly decremented with the pH value. A high sensitivity of $4.32~{\mu }\text{A}$ /mm-pH was obtained. These GaN HEMT structures demonstrated a quick response to the pH changes. It was also investigated that the devices were susceptible toward the aqueous salt solution (NaCl + DI). The percentage change in drain current linearly decreased with decreasing NaCl molar concentration in DI water. We have reported on the change in current with the smaller range of molar concentration of NaCl present in water. Evaluating the sensitivity and response time, we obtained a high sensitivity of 6.48 mA/mm-molar and a response time of 250–350 ms at ${V}_{\text {ds}}= +1$ V. We have also reported on the change in current with the molar concentration of NaCl present in PBS with a high sensitivity of 2.02 mA/mm-molar at ${V}_{\text {ds}}= +5$ V. These outcomes show that the AlGaN/GaN HEMTs are exceptionally promising as a high-sensitivity pH sensor and salinity sensor for biological experiments.

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 BCl3: Cl2 combination. Hence, the Ar addition in the single step etching proved to be more beneficial as compared to the double step etching technique.

In this paper, we have proposed electrothermal modeling of GaN-based HEMT devices. A data-driven approach has been implemented for a temperature range varying from 300 to 600 K, based on one of the core methods of machine learning techniques based on decision tree (DT). The performance of the proposed models was validated through the simulated test examples. The attained outcomes depicted that the developed models predict the HEMT device characteristics accurately depending on the determined mean-squared error (MSE) between the actual and anticipated characteristics. The paper also indicates that the decision tree technique could be specifically beneficial when data are nonlinear and multidimensional, with the different process parameters exhibited profoundly complex interactions.

In this article, we have proposed a "Predictive Current Control" technique for PV fed VSI A "DC-DC Converter" has implemented with "Perturb and Observe MPPT (Maximum Power Point Tracking) algorithm". The "Predictive Current Control" is employed for a 3-phase "Voltage Source Inverter" with "linear and nonlinear loads". A battery is a bidirectional device which can store as well as deliver the power, during storage it is in charging mode and when it delivers the power works at discharging mode, it is connected between the boost converter and inverter. The proposed current control technique will provide fast transient and steady response with lesser harmonics in load currents. The MATLAB/ Simulink platform has used for the modeling and simulation the system and the results obtained are presented.

One-third of total carbon footprint in the world is being caused by conventional combustion-based transportation system. To reduce these carbon footprints various renewable energy sources-based transportation mechanism is innovated with less maintenance cost. Electric vehicle is one of the most prominent among them which uses electricity and provides transportation. Various power conversion methods are used to convert energy from one another form to electrical energy. Various losses occur during the process which leads in CO2 emission and causes harm to the environment. Wide band gap GaN provides better efficient converters and chargers for electrical vehicles to make them more efficient and environment friendly. This paper gives a detailed discussion on GaN for EVs and relevant process for ion-implantation based discrete device. This paper reports on a discrete GaN depletion mode high electron mobility transistor (HEMT) with a breakdown voltage of 200V with a high isolation resistance of 2.89 ×1010 Ohms/sq. and a mobility of 1600 cm2/V.sec. for the of 48V DC-DC power converters employed in Electric vehicles (EVs).

In this paper, we present an investigation of the impact of GaN capping layer and AlGaN layer thickness on the two-dimensional (2D)-electron mobility and the carrier concentration which was formed close to the AlGaN/GaN buffer layer for Al0.25Ga0.75N/GaN and GaN/Al0.25Ga0.75N/GaN heterostructures deposited on sapphire substrates. The results of our analysis clearly indicate that expanding the GaN capping layer thickness from 1 nm to 100 nm prompts an increment in the electron concentration at hetero interface. As consequence of which drain current was additionally increments with GaN cap layer thicknesses, and eventually saturates at approximately 1.85 A/mm for capping layer thickness greater than 40 nm. Interestingly, for the same structure, the 2D-electron mobility, decrease monotonically with GaN capping layer thickness, and saturate at approximately 830 cm2/Vs for capping layer thickness greater than 50 nm. A device with a GaN cap layer didn't exhibit gate leakage current. Furthermore, it was observed that the carrier concentration was first decrease 1.03 × 1019/cm3 to 6.65 × 1018/cm3 with AlGaN Layer thickness from 5 to 10 nm and after that it increases with the AlGaN layer thickness from 10 to 30 nm. The same trend was followed for electric field distributions. Electron mobility decreases monotonically with AlGaN layer thickness. Highest electron mobility 1354 cm2/Vs were recorded for the AlGaN layer thickness of 5 nm. Results obtained are in good agreement with published experimental data.

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 (ρc) 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 ρc value of 5 × 10−5 Ω-cm2 while the ρc 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 Ω-cm2. Different Ni-based stacks with ratio variations were then deposited and compared for thick and thin AlGaN/GaN HEMTs structures. The same value of ρc 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, ρc was found to be increased dramatically for thin AlGaN/GaN HEMTs.

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 Vds = +1 V is obtained.

This work reports on the development of a compact GaN high-electron-mobility transistor (HEMT) based biosensor for an easy and early detection of breast cancer biomarker C-erbB2 in the human cell line. The early-stage detection process includes a reaction of antibody-antigen through the cell line culture of a patient. The developed sensing chip has a two-finger gate structure of 125 µm gate width, and a gate length of 5 µm. In order to functionalize the gold surface of the fabricated sensor, the sensor chip has been immersed into an optimized 1 M aqueous solution of thioglycolic acid at room temperature for 15 h. Various characterization methods such as I–V, EDS, and FTIR confirm the formation of the Au–S complex. The functionalized sensors have been incubated in phosphate buffer saline solution of 200 µg ml−1 C-erbB2 monoclonal antibody for 4 h. Thereafter, the C-erbB2 monoclonal antibody conjugated devices are incubated with human cancer cells positive for C-erbB2 on its cell surface. The biosensor shows a 31% change in drain current for an incubation period of 6 h. The high-resolution biosensing chip (in terms of high drain current levels of the order of mA) is unaffected by noise and eases the circuit for futuristic point of care diagnostics.

In this paper, we discussed the effect of different bias and structures in relation to S-D distance variation on the device electrical and expected biosensing performance. Devices with source to drain length ( $$L_{SD})$$ L S D ) variations from 3.5, 5.0, 8.0, 14.0, 26.0 to $$52~\upmu $$ 52 μ m were simulated at low and high bias voltages. Different structures having gate recess and finger variations were investigated for the complete range of $$L_{SD}$$ L S D variations. Small and very large $$L_{SD}$$ L S D variations in non-recessed structure showed good values of drain current $$(I_{ds})$$ ( I d s ) and transconductances $$(g_{m})$$ ( g m ) at different low and high bias voltages respectively. Therefore expected response time and sensitivity could be improved by choosing a proper bias condition for different biosensing $$L_{SD}$$ L S D lengths. A gate recess structure showed better $$g_{m}$$ g m values at low bias conditions for all $$L_{SD}$$ L S D lengths. However, $$I_{ds}$$ I d s degraded for these structures and hence the expected response time. The non-recessed structure variations in terms of number of fingers and gate width did not change the effective trends in $$L_{SD}$$ L S D variation.

AlGaN/GaN has been considered as a promising candidate for bio-sensing applications due to their outstanding properties. Scaling of gate length and source to gate length plays a key role in the performance of biosensor as it directly influences the device transconductance and hence the sensitivity and response time of biosensors. In this paper, we investigated the effect of variations in gate lengths (1–5 μm) and source to gate length (1–3 μm) to choose the most suitable one for bio sensing applications. Downscaling of gate length (LG) and source to gate length (LSG) improve the device performance, enhancing the drain-current (Ids) and device transconductance. The results of simulations indicate that LG1 μm_LSG1μm with constant LSD configuration shows highest output current 1.01 A/mm, transconductance (gm) 211 mS/mm with lowest value of gate leakage current. Irrespective of LSG, effect of variation in LG follows same trend.

Different stress-free silicon nitride passivation layer designs were simulated using simulation software Silvaco. Different SiNx passivation layer designs (passivation only between the gate-source and gate-drain, passivation edge exactly touching the edges of source and drain contacts and coming over the gate, passivation edges partially covering the source and drain contacts and completely covering the gate, passivation only in the channel area and completely covering the gate) were checked to study their role in GaN HEMTs device improvement process. Resulted Drain current (Ids) was recorded to be the same in all the different designs. A comparatively lower value of transconductance (gm) was observed in the design having passivation layer exactly touching the edges of source and drain contacts and coming over the gate. Therefore this design was not recommendable. Devices suffered with high gate leakage current independent of design types. An introduction of traps in AlGaN layer surprisingly reduced the gate leakage current in such structures.