A 4.69-W/mm output power density InAlN/GaN HEMT grown on sapphire substrate

We report high performance InA1N/GaN HEMTs grown on sapphire substrates. The lattice-matched InA1N/GaN HEMT sample showed a high 2DEG mobility of 1210 cmZ/（V.s） under a sheet density of 2.6 × 10^13 cm^-2. Large signal load-pull measurements for a （2 × 100 μm） x 0.25 μm device have been conducted with a drain voltage of 24 V at 10 GHz. The presented results confirm the high performances reachable by InAIN- based technology with an output power density of 4.69 W/ram, a linear gain of 11.8 dB and a peak power-added efficiency of 48%. This is the first report of high performance InA1N/GaN HEMTs in China's Mainland.

Development of Surface Grating Distributed Feedback Quantum Cascade Laser for High Output Power and Low Threshold Current Density

We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.

Influence of fin architectures on linearity characteristics of AlGaN/GaNFinFETs

We investigate the influence of fin architecture on linearity characteristics of AlGaN/GaNFinFET.It is found that the Fin FET with scaled fin dimensions exhibits much flatter Gm characteristics than the one with long fins as well as planar HEMT.According to the comparative study,we provide direct proof that source resistance rather than tri-gate structure itself dominates the Gm behavior.Furthermore,power measurements show that the optimized FinFET is capable of delivering a much higher output power density along with significant improvement in linearity characteristics than conventional planar HEMT.This study also highlights the importance of fin design in GaN-based FinFET for microwave power application,especially high-linearity applications.

Remarkable average thermoelectric performance of the highly oriented Bi(Te,Se)-based thin films and devices

Bi(Te,Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric(TE)materials due to their high performance at near room tem-perature.Compared with 3D bulks,2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro-and nano-devices.For device applications,high average TE performance over the entire operating temperature range is critical.Herein,highly c-axis-oriented N-type Bi(Te,Se)epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature.The film deposited at~260℃demonstrate a remarkable average power factor(PFave)of~24.4 mW·cm^(-1)·K^(-2)over the tem-perature range of 305e470 K,higher than most of the state-of-the-art Bi(Te,Se)-based films.Moreover,the estimated average zT value of the film is as high as~0.81.We then constructed thin-film TE devices by using the above oriented Bi(Te,Se)films,and the maximum output power density of the device can reach up to~30.1 W/m^(2)under the temperature difference of 40 K.Predictably,the outstanding average TE performance of the highly oriented Bi(Te,Se)thin films will have an excellent panorama of applications in semiconductor cooling and power generation.

Two-dimensional layered architecture constructing energy and phonon blocks for enhancing thermoelectric performance of InSb

InSb is a narrow-bandgap semiconductor with a zinc blende structure and has been wildly applied in photodetectors, infrared thermal imaging, and Hall devices. The facts of decent band structure, ultrahigh electron mobility,and nontoxic nature indicate that InSb may be a potential mid-temperature thermoelectric material. The critical challenges of InSb, such as high thermal conductivity and small Seebeck coefficient, have induced its ultrahigh lattice thermal conductivity, and thus low ZT values. In view of this, we have developed a competitive strategy typified by the cost-efficient nanocompositing of z wt% QSe_(2)(Q = Sn, W). Specifically, the Q_(In)^(+) and Se_(Sb)^(+) point defects were introduced in the In Sb system by nanocompositing the vested two-dimensional layered QSe_(2). In addition, the enlarged valence band maximum of intrinsic WSe_(2)acted as ladders can scatter a fair number of hole carriers, resulting in the relatively enhanced Seebeck coefficient of high temperature. Moreover, the disorderly distributed nanosheets/particles, and dislocations acting as obstacles can effectively delay the heat flow diffusion, inducing the strong scattering of thermal phonons. Consequently, an enhanced power factor of ~33.3 μW cm^(-1)K^(-2) and ZT value of~0.82 at 733 K have been achieved in the 3% WSe_(2)sample,companied with the engineering output power density ω_(max)~233 μW cm^(-1) and thermoelectric conversion efficiency η~5.2%. This artificially designed approach indicated by suited nanocompositing can integrate several engineering strategies such as point defects, nanoengineering, and energy filtering into one, providing a reference to optimize the thermoelectric performance of other thermoelectric systems.