No abstract

Alloying is one of the most common approaches to modulate the properties of semiconductors, such as indium antimonide (InSb) with practical applications in mid-infrared optoelectronics. Thermal conductivity plays a key role in governing the operating performance of devices, and the high-efficiency regulation is of great significance to desirable applications. In this study, we studied the thermal transport properties of InSb, GaSb, and their Ga x In 1−x Sb alloys by solving the Boltzmann transport equation based on first-principles calculations. The thermal conductivity of Ga x In 1−x Sb alloys (x = 0.25, κ = 9.21 Wm −1 K −1 ; x = 0.5, κ = 11.22 Wm −1 K −1 ; and x = 0.75, κ = 15.45 Wm −1 K −1 ) is enhanced compared with that of InSb (κ = 5.15 Wm −1 K −1 ), which is unlike the conventional belief that alloying usually reduces thermal conductivity. Through fundamental analysis of phonon transport properties, the higher phonon group velocity and phonon relaxation time caused by the weak phonon anharmonicity lead to higher thermal conductivity of the Ga x In 1−x Sb alloys. The weakened polarization of Ga x In 1−x Sb alloys occurring in the alloying process generates the increased thermal conductivity, which can be figured out by analyzing the orbital-projected electronic density of states and the electron localization functions. The underlying mechanism of unconventional high thermal conductivity of the Ga x In 1−x Sb alloys in this study would provide guidance for the device applications accompanied by thermal transport.

The giant converse magnetoelectric coupling (GME) was observed in the multiferroic Co40Fe40B20/(011)-0.7Pb (Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructures at room temperature in this investigation. A tunability of magnetization by electric field along the [100] direction was up to-66.7% at-10 Oe bias magnetic fields. Moreover, the non-volatile magnetization switching was found after removal of bipolar electric field. The corresponding remanent magnetic states even without the assistance of bias magnetic fields were stable and could be modulated synchronously by a sequence of pulse electric fields. The 90o rotation of easy axis and non-symmetrical ferroelastic domain switching contributed to the above results. This work is of great significance in designing ultra-low power and non-volatile magnetoelectric memories and other spintronic devices at room temperature.

A top-illuminated circular mesa uni-traveling-carrier photodetector (UTC-PD) is proposed in this paper. By employing Gaussian graded doping in InGaAs absorption layer and InP depleted layer, the responsivity and high speed response characteristics of the device are optimized simultaneously. The responsivity up to 1.071 A/W (the external quantum efficiency of 86%) is obtained at 1550 nm with a 40-µm diameter device under 10-V reverse bias condition. Meanwhile, the dark current of 7.874 nA and the 3-dB bandwidth of 11 GHz are obtained with the same device at a reverse bias voltage of 3 V.

Graphene film has been successfully grown on Cu foil by directly depositing carbon atoms with a solid source molecular beam epitaxy (SSMBE) system. The structural and electronic properties of the graphene sample are characterized by Raman spectroscopy, near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). Results indicate that the graphene has the tubostratic stacking structure.