Trupti Ranjan Lenka

Bio: Trupti Ranjan Lenka is an academic researcher from National Institute of Technology, Silchar. The author has contributed to research in topics: High-electron-mobility transistor & Threshold voltage. The author has an hindex of 15, co-authored 132 publications receiving 828 citations. Previous affiliations of Trupti Ranjan Lenka include National Institute of Standards and Technology.

Characteristics study of 2DEG transport properties of AlGaN/GaN and AlGaAs/GaAs-based HEMT

Abstract: Growth of wide bandgap material over narrow bandgap material, results into a two dimensional electron gas (2DEG) at the heterointerface due to the conduction band discontinuity. In this paper the 2DEG transport properties of AlGaN/GaN-based high electron mobility transistor (HEMT) is discussed and its effect on various characteristics such as 2DEG density, C-V characteristics and Sheet resistances for different mole fractions are presented. The obtained results are also compared with AlGaAs/GaAs-based HEMT for the same structural parameter as like AlGaN/GaN-based HEMT. The calculated results of electron sheet concentration as a function of the Al mole fraction are in excellent agreement with some experimental data available in the literature.

Full-Color InGaN/AlGaN Nanowire Micro Light-Emitting Diodes Grown by Molecular Beam Epitaxy: A Promising Candidate for Next Generation Micro Displays.

Abstract: We have demonstrated full-color and white-color micro light-emitting diodes (μLEDs) using InGaN/AlGaN core-shell nanowire heterostructures, grown on silicon substrate by molecular beam epitaxy. InGaN/AlGaN core-shell nanowire μLED arrays were fabricated with their wavelengths tunable from blue to red by controlling the indium composition in the device active regions. Moreover, our fabricated phosphor-free white-color μLEDs demonstrate strong and highly stable white-light emission with high color rendering index of ~ 94. The μLEDs are in circular shapes with the diameter varying from 30 to 100 μm. Such high-performance μLEDs are perfectly suitable for the next generation of high-resolution micro-display applications.

High performance electron blocking layer-free InGaN/GaN nanowire white-light-emitting diodes.

Abstract: We investigated the effect of coupled quantum wells to reduce electron overflow in InGaN/GaN dot-in-a-wire phosphor-free white color light-emitting diodes (white LEDs) and to improve the device performance. The light output power and external quantum efficiency (EQE) of the white LEDs with coupled quantum wells were increased and indicated that the efficiency droop was reduced. The improved output power and EQE of LEDs with the coupled quantum wells were attributed to the significant reduction of electron overflow primarily responsible for efficiency degradation through the near-surface GaN region. Compared to the commonly used AlGaN electron blocking layer between the device active region and p-GaN, the incorporation of a suitable InGaN quantum well between the n-GaN and the active region does not adversely affect the hole injection process. Moreover, the electron transport to the device active region can be further controlled by optimizing the thickness and bandgap energy of this InGaN quantum well. In addition, a blue-emitting InGaN quantum well is incorporated between the quantum dot active region and the p-GaN, wherein electrons escaping from the device active region can recombine with holes and contribute to white-light emission. The resulting device exhibits high internal quantum efficiency of 58.5% with highly stable emission characteristics and virtually no efficiency droop.

AlGaN/GaN-based HEMT on SiC substrate for microwave characteristics using different passivation layers

Abstract: In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si3N4 and SiO2 passivation layers using technology computer aided design (TCAD) The two-dimensional electron gas (2DEG) transport properties are discussed by solving Schrodinger and Poisson equations self-consistently resulting in various subbands having electron eigenvalues From DC characteristics, the saturation drain currents are measured to be 600 mA/mm and 550 mA/mm for Si3N4 and SiO2 passivation layers respectively Apart from DC, small-signal AC analysis has been done using two-port network for various microwave parameters The extrinsic transconductance parameters are measured to be 1317 mS/mm at a gate voltage of Vgs = −035 V and 1146 mS/mm at a gate voltage of Vgs = −04 V for Si3N4 and SiO2 passivation layers respectively The current gain cut-off frequencies (ft) are measured to be 271 GHz and 2397 GHz in unit-gain-point method at a gate voltage of −04 V for Si3N4 and SiO2 passivation layers respectively Similarly, the power gain cut-off frequencies (fmax) are measured to be 41 GHz and 385 GHz in unit-gain-point method at a gate voltage of −01 V for Si3N4 and SiO2 passivation layers respectively Furthermore, the maximum frequency of oscillation or unit power gain (MUG = 1) cut-off frequencies for Si3N4 and SiO2 passivation layers are measured to be 32 GHz and 28 GHz respectively from MUG curves and the unit current gain, ∣ h21 ∣ = 1 cut-off frequencies are measured to be 140 GHz and 75 GHz for Si3N4 and SiO2 passivation layers respectively from the abs ∣ h21 ∣ curves HEMT with Si3N4 passivation layer gives better results than HEMT with SiO2 passivation layer

Light-emitting diodes

Abstract: Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

Wurtzite-derived polytypes of kesterite and stannite quaternary chalcogenide semiconductors

Abstract: The I(2)-II-IV-VI(4) quaternary chalcogenide semiconductors (e.g., Cu(2)ZnGeS(4), Cu(2)ZnSnS(4), Cu(2)ZnGeSe(4) Cu(2)CdSnSe(4), and Ag(2)CdGeSe(4)) have been studied for more than 40 years but the nature of their crystal structures has proved contentious. Literature reports exist for the stannite and kesterite mineral structures, which are zinc-blende-derived structures, and wurtzite-stannite, which is a wurtzite-derived structure. In this paper, through a global search based on the valence octet rule (local charge neutrality), we report a wurtzite-derived structure corresponding to the kesterite structure, namely, wurtzite-kesterite (space group Pc), which is the ground state for some I(2)-II-IV-VI(4) compounds, but is easily confused with the wurtzite-stannite space group Pmn2(1)) structure. We show that there is a clear relationship between the properties of the wurtzite-kesterite and zinc-blende-derived kesterite structures, as well as between wurtzite-stannite and stannite. Contributions from the strain and Coulomb energies are found to play an important role in determining the structural stability. The underlying trends can be explained according to the size and ionicity of the group-I, -II, -IV, and -VI atoms. Electronic-structure calculations show that the wurtzite-derived structures have properties similar to the zinc-blende-derived structures, but their band gaps are relatively larger, which has also been observed for binary II-VI semiconductors.

Band Gaps of InN and Group III Nitride Alloys

Abstract: We review the fundamental band gaps of wurtzite InN and group III nitride ternary alloys in the light of the recent discovery of the narrow band gap of InN. The results on the composition, temperature and hydrostatic pressure dependence of the band gaps of these alloys are summarized and discussed. The role of the Burstein–Moss shift for the accurate determination of the band gap is emphasized. The impact of the narrow band gap of InN on new device applications of group III nitrides is briefly discussed.