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In order to solve the problem of poor inversion ability of multiple magnetic field sources inside small-scale objects, a multi-magnetic source inversion technology for small-scale objects was proposed. The atomic magnetometer was used to collect the magnetic source signal, the distribution of the magnetic source was inverted based on the theory of weak field, the distribution source model and Gauss-Seidel iterative algorithm were introduced to optimize the solution process, and the forward and inverse model was verified. At the same time, the point source model deconvolution operation was used to improve the spatial resolution of the magnetic source, and the spatial resolution of the system is about 10 mm before deconvolution and less than 4 mm after deconvolution. The results show that the spatial position distribution of the magnetic source inversion is roughly close to the real one, which verifies the correctness of the inversion technology and can be used for the identification of magnetic sources in precision instruments. This research has opened up a new way for the detection of multiple magnetic sources inside some precision instruments. [ABSTRACT FROM AUTHOR]

Diamond as an ultra-wide band gap semiconductor material shows excellent properties in thermal conductivity, carrier mobility and breakdown field strength, and has broad application prospects in the field of power electronics. The realization of p-type and n-type conduction is essential to fabricate diamond electronic devices. Between them, the development of p-type diamond is relatively mature, and boron is the mainstream doping element. However, the hole mobility decreases rapidly at a high doping concentration. The main doping element of n-type diamond is phosphorus. At present, there are still challenges such as deep impurity level, large ionization energy, and defects in diamond crystals after doping, resulting in low carrier concentration and mobility, and the resistivity is difficult to meet the requirements of devices. Therefore, the realization of high quality p-type and n-type diamond has become the focus of researchers. This paper mainly introduces the unique physical properties of single crystal diamond, outlines the basic principles and key parameters of the chemical vapor deposition method and ion implantation method of doping, then reviews the research progress on the p-type and n-type doping of single crystal diamond films by the two methods, systematically summarizes the facing problems and the prospects of future development. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) high electron mobility transistor (HEMT) has attracted much attention due to its high breakdown field strength, low on-resistance and high conversion efficiency, and it is expected to be applied in power electronics systems. However, its high power density and high frequency characteristics bring great challenges to packaging technology. The parasitic inductance parameters in the package of traditional silicon power electronic devices is large, which will cause switch oscillation and other problems, so that the excellent performance of GaN cannot be fully utilized. In addition, the thermal management ability of the package determines the reliability of the power device. If the self-heating effect of the device cannot be well solved, its performance will be reduced, and even the chip will be burned. On the basis of explaining the switching oscillation and thermal management problems caused by traditional packaging technology applied to gallium nitride power electronic devices, the research progress of GaN packaging technology aiming at the above problems are reviewed in detail in this paper, including by optimizing the control circuit, reducing Lg inductancing, improving Rg inhibition of dv/dt, increasing ferrite beads on the gate electrode, PCB layout optimization and increasing magnetic flux offset method to solve the problem of switch oscillation caused by the parasitic inductance, the application of high thermal conductivity material of diamond in devices thermal management, improvement of device package structure and other heat dissipation technologies. [ABSTRACT FROM AUTHOR]

The chips of vertical cavity surface emitting laser (VCSEL) with different positions of cavity mode were designed and prepared for 894.6 nm VCSEL with wavelength-stabilized output in high temperature environment. The influence of cavity mode position on lasing wavelength is studied by testing and analyzing the cavity mode position, output wavelength and temperature drift coefficient of VCSEL. It is found that the lasing wavelength of VCSEL has a linear relation with cavity mode. A structure of VCSEL with cavity mode at 890.5 nm was designed. VCSEL chips which output wavelength is 894.6 nm in 85 ℃ high temperature environment were prepared. The results show that the desired output wavelength of VCSEL chips can be obtained by controlling the position of cavity mode. [ABSTRACT FROM AUTHOR]