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.

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Light-emitting diodes

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.

http://absimage.aps.org/image/MAR11/MWS_MAR11-2010-004648.pdf

Wurtzite-derived polytypes of kesterite and stannite quaternary chalcogenide semiconductors

A survey of Gallium Nitride HEMT for RF and high power applications

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.

Band Gaps of InN and Group III Nitride Alloys

The theoretical approach

Investigation of structural, morphological, and optoelectronic properties of Ga-doped TiO2 nanoparticles for electron transport layer in solar cell applications: An experimental and theoretical study

In this work, an InGaN/GaN multi-quantum well light emitting diode is designed with different kinds of prestrain layers (InGaN) inserted between the active region and n-GaN layer to demonstrate the effects of piezoelectric polarization on GaN-based LEDs. The device describes a GaN buffer layer which promotes charge injection by minimizing energy barrier between electrode and active layers. Compared to the conventional LED, more than 48.47% enhancement in the efficiency of the LED with prestrain layer can be observed which is attributed to the reduction of polarization field within MQW regions. The proposed device attains a high-efficiency of 81.94%, and minimized efficiency droop of 3.848% at an injection current of 10 mA with 16% In composition and has high-luminous power in the spectral range.

Influence of Prestrained Graded InGaN interlayer on the Optical Characteristics of InGaN/GaN MQW-based LEDs

Carrier transport mechanism in bottom gate thin‐film transistor with SnO as active layer for CMOS displays

Modeling and Simulation of CZTS Thin-Film Solar Cell for Efficiency Enhancement

In the current scenario of high-speed electronics technology, many application areas—broadband Internet access, fifth-generation (4G/5G) mobile systems, and cutting-edge military applications—are realizing very-fast to reality. To cater these ever-increasing demands, radio-frequency (RF) and microwave power amplifiers are in prime-attention, and will be constantly evaluated on price versus performance metrics. Ultra-wide bandgap (UWBG) high electron mobility transistors (HEMTs) are promising candidates for switching power applications owing to very-high breakdown strength of the material. And higher values of energy band gap (Eg) and electron mobility enabled low on-resistance (RON) guarantees superior power handling capability. UWBG HEMTs having two-dimensional electron gas (2DEG) channel with high carrier concentration and high electron mobility are fast gaining space in high frequency and power switching applications. Also, these UWBG materials having large optical phonon energy, Eop ~92 meV (GaN), ~45 meV (β-Ga2O3) make them most suitable semiconductor materials for the imminent terahertz (THz, 1012 Hz) frequency applications: THz imaging and spectroscopy. In this paper, we present latest technological developments of the gallium nitride (GaN)- and beta-phase of gallium oxide (β-Ga2O3)-based HEMTs, with careful and quantitative investigation of their suitability toward radio frequency (RF), high power device applications, and THz emerging applications.

Trupti Ranjan Lenka

Papers

Investigation of structural, morphological, and optoelectronic properties of Ga-doped TiO2 nanoparticles for electron transport layer in solar cell applications: An experimental and theoretical study

Influence of Prestrained Graded InGaN interlayer on the Optical Characteristics of InGaN/GaN MQW-based LEDs

Carrier transport mechanism in bottom gate thin‐film transistor with SnO as active layer for CMOS displays

Modeling and Simulation of CZTS Thin-Film Solar Cell for Efficiency Enhancement

RF performance of ultra-wide bandgap HEMTs