We report on a growth of nearly lattice-matched InAlN/GaN heterostructures on 4H–SiC substrates by pulsed metal organic chemical vapor deposition, and an excellent device characteristic of high electron mobility transistors (HEMTs) fabricated on these InAlN/GaN heterostructures. The electron mobility is 1032 cm2/V s together with a high two-dimensional-electron-gas density of 1.59×1013 cm−2 for the In0.17Al0.83N/AlN heterostructures. HEMTs with gate dimensions of 0.5×50 μm2 and 3 μm source-drain distance exhibits a maximum drain current of 1 A/mm, a maximum extrinsic transconductance of 310 mS/mm, and current gain and maximum oscillation cutoff frequencies of 18 GHz and 39 GHz, respectively.

The graded AlGaN:Si back barrier can form the majority of three-dimensional electron gases (3DEGs) at the GaN/graded AlGaN:Si heterostructure and create a composite two-dimensional (2D)–three-dimensional (3D) channel in AlGaN/GaN/graded-AlGaN:Si/GaN:C heterostructure (DH:Si/C). Frequency-dependent capacitances and conductance are measured to investigate the characteristics of the multi-temperature trap states of in DH:Si/C and AlGaN/GaN/GaN:C heterostructure (SH:C). There are fast, medium, and slow trap states in DH:Si/C, while only medium trap states exist in SH:C. The time constant/trap density for medium trap state in SH:C heterostructure are (11 μs–17.7 μs)/(1.1 × 1013 cm−2·eV−1–3.9× 1013 cm−2·eV−1) and (8.7 μs–14.1 μs)/(0.7× 1013 cm−2·eV−1–1.9× 1013 cm−2·eV−1) at 300 K and 500 K respectively. The time constant/trap density for fast, medium, and slow trap states in DH:Si/C heterostructure are (4.2 μs–7.7 μs)/(1.5× 1013 cm−2·eV−1–3.2× 1013 cm−2·eV−1), (6.8 μs–11.8 μs)/(0.8× 1013 cm−2 · eV−1–2.8× 1013 cm−2 · eV−1), (30.1 μs–151 μs)/(7.5× 1012 cm−2 · eV−1–7.8× 1012 cm−2 · eV−1) at 300 K and (3.5 μs–6.5 μs)/(0.9× 1013 cm−2 · eV−1–1.8× 1013 cm−2 · eV−1), (4.9 μs–9.4 μs)/(0.6× 1013 cm−2 · eV−1–1.7× 1013 cm−2 · eV−1), (20.6 μs–61.9 μs)/(3.2× 1012 cm−2 · eV−1–3.5× 1012 cm−2·eV−1) at 500 K, respectively. The DH:Si/C structure can effectively reduce the density of medium trap states compared with SH:C structure.

We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped with a transparent protective layer), using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed system. The numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak loss. This may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.

An AlGaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of ( 102) and (002) X-ray diffraction rocking curves. With an increase in the Si-doped concentration in the GaN wells, the full width at half maximum of the (102) rocking curves decreases, while that of the (002) rocking curves increases. A significant increase of the full width at the half maximum of the (002) rocking curves when the doping concentration reaches 2.5 × 10 19 cm −3 indicates the substantial increase of the inclined threading dislocation. High level doping in the AlGaN/GaN superlattice can greatly reduce the biaxial stress and optimize the surface roughness of the structures grown on the top of it.

Pulsed metal organic chemical vapor deposition is introduced into the growth of InGaN channel heterostructure for improving material qualities and transport properties. High-resolution transmission electron microscopy imaging shows the phase separation free InGaN channel with smooth and abrupt interface. A very high two-dimensional electron gas density of approximately 1.85 × 10 13 cm −2 is obtained due to the superior carrier confinement. In addition, the Hall mobility reaches 967 cm 2 /V•s, owing to the suppression of interface roughness scattering. Furthermore, temperature-dependent Hall measurement results show that InGaN channel heterostructure possesses a steady two-dimensional electron gas density over the tested temperature range, and has superior transport properties at elevated temperatures compared with the traditional GaN channel heterostructure. The gratifying results imply that InGaN channel heterostructure grown by pulsed metal organic chemical vapor deposition is a promising candidate for microwave power devices.