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The effect of carbon doping on the structural and electrical properties of GaN buffer layer of AlGaN/GaN high electron mobility transistor (HEMT) structures has been studied. In the undoped HEMT structures, oxygen was identified as the dominant impurity using secondary ion mass spectroscopy and photoluminescence (PL) measurements. In addition, a notable parallel conduction channel was identified in the GaN buffer at the interface. The AlGaN/GaN HEMT structures with carbon doped GaN buffer using a CBr4 beam equivalent pressure of 1.86 × 10−7 mTorr showed a reduction in the buffer leakage current by two orders of magnitude. Carbon doped GaN buffers also exhibited a slight increase in the crystalline tilt with some pits on the growth surface. PL and Raman measurements indicated only a partial compensation of donor states with carbon acceptors. However, AlGaN/GaN HEMT structures with carbon doped GaN buffer with 200 nm thick undoped GaN near the channel exhibited good 2DEG characteristics.

Dielectric investigations of hydrogen bonded complexes of Enanthamide and Valeramide with 4-bromophenol, 4-chlorophenol, 4-iodophenol and 4-fluorophenol in benzene were done at 303K, using a J-band (7.22GHz) microwave bench and dielectric relaxation setup. The permittivity of amides with halogenated phenol binary mixtures was measured in the microwave frequency range at temperatures ranging from 298K to 323K. At microwave frequencies; dielectric relaxation of ternary mixes of polar liquids in nonpolar fluids has been explored. Such investigations give useful information about the intermolecular and intramolecular interactions of solutes and solvent molecules. The dipole meter had a measurement frequency of 2MHz. The different parameters of dielectric, relaxation time (τ 0 ) and the dipole moment (μ) has been evaluated using the single-frequency concentration Higasi approach. The fact that the relaxation time and molar free energy activation of the 1:1 molar ratio are greater than those of other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3) confirms the presence of a 1:1 complex structure between the studied systems, as well as a complex formation between the free hydroxyl group of phenols and the carbonyl group of amides. The dielectric relaxation energy parameters (ΔFε, ΔHε and ΔSε) of amides with halogenated phenols in benzene have been computed and compared with the related viscosity parameters. A comparison of these two sets of characteristics reveals that dielectric relaxation, like viscous flow, may be thought of as rate process.

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