D. Mahaveer Sathaiya

Bio: D. Mahaveer Sathaiya is an academic researcher. The author has contributed to research in topics: Thermionic emission & Leakage (electronics). The author has an hindex of 3, co-authored 4 publications receiving 230 citations.

Mechanism of the reverse gate leakage in AlGaN/GaN high electron mobility transistors

Abstract: The off-state gate current in AlGaN/GaN high electron mobility transistors is shown to arise from two parallel gate to substrate tunneling paths: a direct path, and a path via deep traps, which are distributed throughout the AlGaN layer and spread over an energy band. A model to calculate this current is given, which shows that trap-assisted tunneling dominates below T∼500 K, and direct tunneling (thermionic field emission) dominates at higher temperatures. A model fit to experimental results yields the following fabrication process sensitive parameters: trap concentration of ∼1013–1015 cm−3, and trap bandwidth of ∼50%–70% of the barrier height located 0.4–0.55 V below the conduction band edge.

Thermionic trap-assisted tunneling model and its application to leakage current in nitrided oxides and AlGaN∕GaN high electron mobility transistors

Abstract: We propose two models of electron tunneling from metal to a semiconductor via traps. In addition to the electrons below the metal Fermi level, the models also include the thermally activated electrons above the Fermi level. The first model is called generalized thermionic trap-assisted tunneling (GTTT), which considers tunneling through both triangular and trapezoidal barriers present in metal insulator semiconductor (MIS) structures. The second model is called thermionic trap-assisted tunneling (TTT), which considers tunneling through triangular barriers present in modern Schottky junctions. The GTTT model is shown to predict the low field leakage currents in MIS structures with nitrided oxide as insulator, and the TTT model is shown to predict the reverse gate leakage in AlGaN∕GaN high electron mobility transistors.

Unified closed-form model of thermionic-field and field emissions through a triangular potential barrier

Abstract: We report a simple closed-form model of the total emission through a triangular potential barrier due to thermionic field emission (TFE) and field emission (FE). Such a model has not been derived previously, since the energy distribution function of emitted electrons is not analytically integrable. We overcame this difficulty using a geometrical approximation of the integration operation. Our model so derived reveals the energy location and spread of the emission, which allow estimation of the emission through any fraction of the barrier. It also yields a characteristic field parameter in terms of the barrier height, temperature, and effective mass, which can be used to identify the TFE, FE, and TE regimes of device operation.

A model for the high field leakage current in nitrided oxides

Abstract: The enhanced conduction at low fields (<4MV∕cm) in metal-insulator semiconductor structures having nitrided oxides was recently explained using a generalized thermionic trap-assisted tunneling model. In the present work, we show that the same model can predict both high and low field leakage currents if we assume that a fraction (∼35%) of the insulator thickness located next to the metal-insulator junction is devoid of traps.

Comprehensive Physics Based TCAD Model for 2D MX2 Channel Transistors

Abstract: For the first time, a comprehensive TCAD model is developed to unambiguously extract key device parameters: contact resistance (Rc), channel mobility (μCH), Schottky barrier height (SBH), & Dit from experimental data on back-gate (BG) transistors with MX2 channel. The model is tested and validated against three different data sets with different contact metal, quality of channel, contact, and interfaces. Using model's output, we analyze the accuracy of Rc and μCH extracted by the TLM method and provide guidance on the limits of its applicability. Finally, the model is used to project contact requirements (SBH ~ 0eV, high doping density >2e13cm-2) for performant, scaled transistors with 2D material channel in stacked nanosheet configuration.

Control of Threshold Voltage of AlGaN/GaN HEMTs by Fluoride-Based Plasma Treatment: From Depletion Mode to Enhancement Mode

Abstract: This paper presents a method with an accurate control of threshold voltages (Vth) of AlGaN/GaN high-electron mobility transistors (HEMTs) using a fluoride-based plasma treatment. Using this method, the Vth of AlGaN/GaN HEMTs can be continuously shifted from -4 V in a conventional depletion-mode (D-mode) AlGaN/GaN HEMT to 0.9 V in an enhancement-mode AlGaN/GaN HEMT. It was found that the plasma-induced damages result in a mobility degradation of two-dimensional electron gas. The damages can be repaired and the mobility can be recovered by a post-gate annealing step at 400 degC. At the same time, the shift in Vth shows a good thermal stability and is not affected by the post-gate annealing. The enhancement-mode HEMTs show a performance (transconductance, cutoff frequencies) comparable to the D-mode HEMTs. Experimental results confirm that the threshold-voltage shift originates from the incorporation of F ions in the AlGaN barrier. In addition, the fluoride-based plasma treatment was also found to be effective in lowering the gate-leakage current, in both forward and reverse bias regions. A physical model of the threshold voltage is proposed to explain the effects of the fluoride-based plasma treatment on AlGaN/GaN HEMTs

Deep-Level Characterization in GaN HEMTs-Part I: Advantages and Limitations of Drain Current Transient Measurements

Abstract: This paper critically investigates the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation. The article is divided in two parts within Part I. 1) We analyze how the choice of the measurement and analysis parameters (such as the voltage levels used to induce the trapping phenomena and monitor the current transients, the duration of the filling pulses, and the method used for the extrapolation of the time constants of the capture/emission processes) can influence the results of the drain current transient investigation and can provide information on the location of the trap levels responsible for current collapse. 2) We present a database of defects described in more than 60 papers on GaN technology, which can be used to extract information on the nature and origin of the trap levels responsible for current collapse in AlGaN/GaN HEMTs. Within Part II, we investigate how self-heating can modify the results of drain current transient measurements on the basis of combined experimental activity and device simulation.

Ferroelectric polarization-leakage current relation in high quality epitaxial Pb ( Zr , Ti ) O 3 films

Abstract: Leakage current measurements were performed on epitaxial, single-crystal quality $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$ films with thicknesses in the $50--300\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ range. It was found that the voltage behavior of the leakage current has a minor dependence on thickness, which rules out the space-charge limited currents as main leakage source. Temperature-dependent measurements were performed to obtain more information on the transport mechanism through the metal-ferroelectric-metal (MFM) structure. The results are analyzed in the frame of interface-controlled Schottky emission. A surprisingly low value of only $0.12--0.13\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ was obtained for the potential barrier, which is much smaller than the reported value of $0.87\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ [I. Stolichnov et al., Appl. Phys. Lett. 75, 1790 (1999)]. The result is explained by the effect of the ferroelectric polarization on the potential barrier height. The low value of the effective Richardson constant, of the order of ${10}^{\ensuremath{-}7}--{10}^{\ensuremath{-}6}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{cm}}^{2}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{2}$, suggests that the pure thermionic emission is not the adequate conduction mechanism for epitaxial MFM structures. The true mechanism might be interface-controlled injection, followed by a low mobility drift through the film volume.

Leakage mechanism in GaN and AlGaN Schottky interfaces

Abstract: Based on detailed temperature-dependent current–voltage (I–V–T) measurements the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed. The experiments were compared to calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation method reproduced the experimental I–V–T characteristics of the GaN and AlGaN Schottky diodes, and gave excellent fitting results to the reported Schottky I–V curves in GaN for both forward and reverse biases at different temperatures. The present results indicate that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces.

Electronic surface and dielectric interface states on GaN and AlGaN

Abstract: GaN and AlGaN have shown great potential in next-generation high-power electronic devices; however, they are plagued by a high density of interface states that affect device reliability and performance, resulting in large leakage current and current collapse. In this review, the authors summarize the current understanding of the gate leakage current and current collapse mechanisms, where awareness of the surface defects is the key to controlling and improving device performance. With this in mind, they present the current research on surface states on GaN and AlGaN and interface states on GaN and AlGaN-based heterostructures. Since GaN and AlGaN are polar materials, both are characterized by a large bound polarization charge on the order of 1013 charges/cm2 that requires compensation. The key is therefore to control the compensation charge such that the electronic states do not serve as electron traps or affect device performance and reliability. Band alignment modeling and measurement can help to determi...