Liangliang Tang

Bio: Liangliang Tang is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Diffusion (business) & Surface diffusion. The author has an hindex of 5, co-authored 5 publications receiving 63 citations.

The intrinsic relationship between the kink-and-tail and box-shaped zinc diffusion profiles in n-GaSb

Abstract: Different diffusion sources were used to study Zn diffusion in n-GaSb. We found that the Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface diffusion fronts in Zn profiles, thus converting the kink-and-tail-shaped profile to the box-shaped profile. Our analysis demonstrated that both the surface and the tail regions in the kink-and-tail profiles showed high-quality regularities. The analysis also revealed that the formation mechanism of the box profiles is the same as that of the tail region of the kink-and-tail profiles. The similarities of the photoluminescence signals between the main region of the box profiles and the tail region of the kink-and-tail profiles substantiated our findings.

Identification of the dissociative and kick-out diffusion mechanisms of Zn diffusion in GaAs by photoluminescence analysis

Abstract: Most investigations on Zn diffusion in GaAs were processed using the Zn–As alloy sources to prevent the As atoms from escaping GaAs wafers, while we found that the Zn diffusion would change fundamentally if Zn–Ga alloy sources were used. The Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface region in Zn profiles, thus converting a kink-and-tail profile into a box profile. The photoluminescence (PL) analysis was used to identify the diffusion mechanisms. The Ga vacancy defects were found in the surface region of the kink-and-tail profile, indicating that the dissociative mechanism dominated; the PL spectrum in the tail region of kink-and-tail profile and the main region of box profile showed the same signals, no Ga vacancy defects were found, thus the kick-out mechanism dominated.

Experimental and theoretical investigation of zinc diffusion in N-GaSb

Abstract: Zinc diffusion process in N-GaSb was studied with excessive, appropriate and insufficient quantity of diffusion source (zinc pellets). Kink-and-tail type zinc concentration profiles obtained with appropriate zinc pellets quantity were successfully simulated using the assumption that the vacancy mechanism mediated by V Ga 0 and kick-out mechanism mediated by I Ga + take effect at the same time. It is found out that for diffusion temperature from 460°C to 500°C, the zinc surface concentration of the diffused samples has nearly no change and the logarithmic value of the zinc surface diffusion coefficient is linear with the reciprocal value of diffusion temperature; when the diffusion temperature is constant, both the zinc surface concentration and diffusion coefficient do not change with diffusion time.

Micro-scale energy harvesting devices: Review of methodological performances in the last decade

Abstract: Power harvesting devices which harness ambient surrounding energies to produce electricity could be a good solution for charging or powering electronic devices. The main advantages of such devices are that they are ecologically safe, portable, wireless, and cost effective and have smaller dimensions. Most of these power harvesting devices are realized by utilizing the microelectromechanical systems (MEMS) fabrication techniques. In this paper, the capabilities and efficiencies of four micro-power harvesting methods including thermoelectric, thermo-photovoltaic, piezoelectric, and microbial fuel cell renewable power generators are thoroughly reviewed and reported. These methods are discussed in terms of their benefits and applications as well as their challenges and constraints. In addition, a methodological performance analysis for the decade from 2005 to 2014 are surveyed in order to discover the methods that delivered high output power for each device. Moreover, the outstanding breakthrough performances of each of the aforementioned micro-power generators within this period are highlighted. From the studies conducted, a maximum energy conversion of 2500 mW cm −2 is reached by thermoelectric modules. Meanwhile, thermo-photovoltaic devices achieved a rise in system efficiency of up to 10.9%. Piezoelectricity is potentially able to reach a volumetric power density of up to 10,000 mW cm −3 . Significantly in microbial fuel cell systems, the highest power density obtained reached up to 6.86 W m −2 . Consequently, the miniaturized energy harvesters are proven to have credibility for the performance of autonomous power generation.

Unidirectional radiative heat transfer with a spectrally selective planar absorber/emitter for high-efficiency solar thermophotovoltaic systems

Abstract: A high-efficiency solar thermophotovoltaic (STPV) system has been demonstrated using spectrally selective planar absorber/emitter systems and a GaSb TPV cell In this study, a novel approach for designing the STPV system based on the efficiency of unidirectional radiative heat transfer has been introduced To achieve high extraction and photovoltaic conversion efficiencies, the spectrally selective absorber/emitter based on a coherent perfect absorber composed of a thin molybdenum layer sandwiched between hafnium layers was applied The extraction efficiency was further investigated with respect to the absorber/emitter area ratio The experimental efficiency of STPV reached 51% with the area ratio of 23

Performance Improvement of the GaSb Thermophotovoltaic Cells With n-Type Emitters

Abstract: GaSb cells are commonly fabricated using Zn diffusion into n-GaSb, and in this paper they have been designed inversely using Te diffusion into unintentionally p-doped GaSb. Numerical simulation is used to analyze the cell performance. We found that a GaSb cell with n-type emitters showed a significantly higher output power density compared with that of the cell with p-type emitters under 1500 K-blackbody radiation. The performance improvement is owing to the good matching of the diffusion length of minority carriers with the depth of their moving regions. Several parameters that affect the cell performance were analyzed, such as doping depth, substrate thickness, and surface recombination velocity. The cell performance was evaluated under low temperature radiations and found to have huge potentials for the use in low-temperature thermophotovoltaic systems.

High-Efficiency Thermophotovoltaic System That Employs an Emitter Based on a Silicon Rod-Type Photonic Crystal

Abstract: Thermophotovoltaic systems in principle enable utilization of heat that is usually regarded as wasted energy. However, the wavelength selectivity of the thermal emitter required for high efficienci...